Your math doesn't add up, they didn't start at the earnings they have now and they did complete and fully release one game already -
Overgrown: Genesis
While Claire Quest has changed and grown a lot over the past 6 years, the current game is massive you'd need 20+ hours if not more to see all the current content
The newest update alone already adds a further 2 new h-scenes, 2 new updated h-scenes (overhauls) and a new questline.
And not like Overgrown Genesis is even a small project it is quite a big game as well with 3 different endings even and multiple h-scene varieties depending again - on your branching choices.