No, my bad I saw it spelled out on a different game of yours. $25 is the brand new update price but it goes down the closer it gets to new update time.
if you look at some of the devs other projects, you can see that in the dev log they state that the price is 25 at release, then it goes down to 19 a week later, 10, a week after that and then when the next release, it's free. Presumably it's the same for all games so for the newer games the dev just stopped bothering to spell that out over and over again. Also I think I remember there being something about it being a one time payment, because you buy the game and then there are updates to it. Judging by the amount of content in each release it seems that the high price is somewhat justified but you're not obligated to pay it, you can just get each release a month late.
Look. Version .5 comes out. For a week or 2, it costs 25. For a week after that it's cheaper, because it's not immediate. Then cheaper still. then update .6 comes out and you can download update .5 for free. And like I said, this information is in the log of some of the devs older games on this site. Just look through those and you'll have a more precise description of the process. Either way, the payment is optional. Many devs work like this, you can pay for the fresh new content, (which funds future production of the game), or you can just wait a month for when it becomes free because there's a newer update. True this is a higher than average price, but it's still the same process as most other adult game developers.