I can tell you have NOT actually looked at AVN prices on Steam in like a decade...
Rebel Duet and MWNeus both released at 10$ with adequate regional pricing and no "extra" content. Bought both.
Here we have 13$ base game with 4$ DLC, and scummy dev famous for reworks.
Not to mention that some games like
Hooligan Crusoe being sold for 2$ and still making a bank, while offering free updates every month, because of sheer amount of purchases.
Some devs just way too greedy for their own good, and forget that porn games have to compete with acutal games being sold for dirt cheap on Steam. Battlefield 4 is like a 4$ right now.
Imagine thinking that your 500 extra renders worth a price of AAA multiplayer game?