Ok, I had my good night’s rest!
So first off:
If you’ve already reached level 100 then the limiting factor for your builds going forward is not the level, it’s the equipment. LE’s system is surprisingly lenient for the last few passive points, they make not a lot of difference (unless you decide to take away the core functional ones, but that isn’t smart
)
Your second point is fine… but given you’ve already reached level 100… isn’t that nothing else then a progression skip for the campaign then? Because outside of a campaign skip there is no reasonable function here.
As for your third point… if you’ve already got a character at the mastery finished at 100… then you got a character finished at 3 masteries, because you can switch masteries. Hence it’s class-specific, not mastery specific already. ‘No mastery swap’ is not a feasable thing… unless you give players a specific warning ‘if you switch mastery you’ll not be able to unlock buying concurrent characters for this mastery at level 100 when you reach it’. Something that will make people hesitant and reduce the respective quality of the experience when they reach that situation, suddenly feeling limited where there was supposed to be no limits in design anymore (after those limits were removed ill-suitedly… but that’s another topic).
Then there’s also the question of ‘why?’… you have the option the respec at that point already which removes the need for buying yourself up to another char in the first place.
As for the pricing range… 1 mil? That’s far too low. This level of power is at least a 50-100 mil gold functionality. Not to speak that Gold is absolutely ill-suited for the job anyway given the sheer magnitude of difference between CoF and MG in acquisition rate.
Now to the core premise behind it:
‘Leveling feel like it sucks, hence I don’t want to level’.
Ok! Fair!
What part of the leveling process is the thing that you didn’t enjoy?
The repetition? Then sorry, for variety you need repetition, otherwise the product has no staying power long-term. So that cannot be done because of it.
You state the following, which is:
Which yes… fair!
But that’s also not a progression issue… it’s a character limit aspect since you cannot keep endless characters. We got 25 slots and 15 masteries… so at best you can have 2/3rd of the masteries with 2 different builds, and that’s it anyway. And that includes all game-modes together.
So… if you wanna play Cycle and you’re a Legacy player as well then you already can only have a single char per mastery anyway… as otherwise? Your SSF experience… your HC experience… your Cycle experience… there’s no space for the characters anyway.
The next thing is: Why two of every mastery? You’re not even supposed to rush through this way. And the time needed isn’t that much anyway. The biggest ‘hurdle’ in gameplay feeling are progression of corruption for the characters… and the campaign section. Both have significant options to be reduced in scale, a level 95 character in 10 hours is nothing major to create in LE actually, and level 100 is not a major boon by then, maybe 5% total power unless the equipment suuuucks.
Yep, that would be a much better option, absolutely so!
Those systems work well… but only in regards to games which focus on longevity in grinding of some form.
So LE can’t make good use of it anyway.
Welcome, me! I’m extremely reluctant to create alts since I don’t enjoy re-doing processes. Sooner or later I do it anyway and expand my options slowly this way… but I’m generally a ‘1 character forever player’.
I’ve played my Tornado Shot Deadeye in PoE for around 5000 hours now, a good 3000 hours farming in maps. Why? Cause I enjoy the process. Everything else of my 10k playtime there is bossing and testing other characters over time, most being dropped again.
If you do not enjoy the process… then the product is not for you. It’s always that simple.
I don’t enjoy the process of leveling secondary characters… I’m not the core audience of any mechanics focusing on replaying characters hence as it reduces my enjoyment.
Hence I need longevity mechanics in a game… and nowadays? A good ARPG has to provide both.
Hence I see the issue as LE not providing enough value in playing singular characters long-term while keeping the respective enjoyment of playing it alive.
Isn’t it more reasonable to play Legacy then and switch between builds on the char with the respective mastery? 1 Tab for a build… put all of it in, take up new gear and start the farming process for it then and there at level 100 with good blessing unlocks as well.
In Cycle this doesn’t make sense anyway as basically nobody would use it, 99,99% of people don’t reach level 100 and get the urge to replay the same mastery to level 100 then rather then simply respeccing.
And value acquisition in Legacy at least provides you with realistic long-term means of respeccing anyway.
I really don’t see the target audience for this change… maybe 3-4 people total would actually profit in a serious way?
The change is so insignificant (and has downsides for perception as well if introduced) that in a list of 1000 things to change it’s somewhere at 995 in priority 
You’re right, a low number is not meaningless… depending on the impact this specific group of players has for the game.
That’s why end-game focus is so high despite the majority never playing in it. The minority makes the vast chunk of revenue and it keeps the product alive as well long-term, right?
But the target you’re setting is a fraction of this fraction and then another fraction of that. There is a cutoff line when invested effort and the respective results are not congruent anymore. And this suggestion clearly is one of those, not to speak of either screwing over people which switch mastery along the way (as you stated you have to achieve it without mastery changing to 100, right?) or giving a warning notice to vastly more people and causing potential choice paralysis at that moment then the total amount of people even getting into the position to use the mechanic you suggest, which is a detrimental situation to exist.
Developing uber abby was a waster of time!
Absolutely so 
The focus of the development went absolutely awry when EHG decided to make the uber boss and it’s caused massive detriment to the game since then.
Depends, there’s 2 sides to this actually.
At one hand… a significant portion of players in ARPGs are goal-focused. Reach goal? Stop playing!
Level 100 is one such significant goal, that’s why several games in the genre tend to make it very hard to reach this point. It’s to keep players engaged longer.
There’s even been a discussion around this specific process with streamers once, which pushed of a bigger discussion on Reddit as much as I remember (PoE Reddit) where people relatively regularly stated that ‘yes, the enjoyment drops when I reach level 100’ actually.
So it seems to be a surprisingly significant portion of players which have this feeling.
So hence we gotta think about it… which is more likely? Someone who looses motivation upon reaching level 100 as their brain says ‘progression done, fun over!’ or someone who goes ‘Need all masteries on level 100… multiple times or no fun!’.
Because it’s presented like utter shit in the game.
It’s not well visible, it doesn’t get explained properly and it feels absolutely and utterly choppy to do.
And that’s for first-time characters and follow-up ones the same actually.
A first-time character gets uselessly sent to the dungeon entrance without having a key, which is a shitty time-waster.
A follow-up character might remember the experience on not even go there, not realizing there is a skip.
To see the skip you need to remember that simply portaling out isn’t the only way to go after finishing the dungeon as well.
Good design would shove this option only when available into the face of the player in some way/shape or form. Which it doesn’t. People literally forget it exists still.
And those using it actively? 2 hour campaign playthrough is absolutely possible, 4 hours is on the high side of play-time when using the skip. Then you are in end-game, with the itemization progression and gradual leveling… as expected and supposed.
So it’s the presentation of the skip which needs to primarily be worked on, not even the functionality.