The quantity of revenue channel causes automatic increase of revenue commonly.
More options means ‘something’ entices a person to spend money should they ever be willing to.
That paid char slot which basically is no effort to code in? For 1% of the playerbase? Meaning around 300k individuals playing in a Cycle? Means 3000 sales. If each sale is 5€ then that means 15000€ revenue solely from that. And the next Cycle? Maybe 5000€… then again… and again… and again.
The concept of sustainability is to create many small revenue streams. Many stream create a torrent. Individually neglecible… in totality a huge sum.