You are right. I think both the fansly and patreon are just a different audience, but in some ways both have their pros and cons. You say that the $200 dollars is worth it, but for some really picky people (like me), they might not be happy with all the 4 sets or characters of a particular month, so they may not feel like it's worth it to pay that much. These people can more easily pick and choose on the fansly which sets they want to support or not. Unfortunately it's not the same sets, so you are very right in what you're saying, especially about the quality.I totally get your point, but it is a really niche case, because it would apply to someone who just wants to see her tits once and be done with it. Then there would be the extra niche case where you would purchase a fansly set because she is cosplaying your favorite anime char.
Any other scenario would be from people who actively support her and her stuff and are most likely purchasing more than 1 set a month from her fansly, so saying that they would only "purchase one and be happy with it" is already out of the question.
You are also forgetting about something, her fansly sets were the most leaked content up to march 2023. So if you really just wanted to see her tits there is more than enough material out there for that.
At this point if you really want you money's worth just save enough for a 200$ tier for a month and you will be more than happy with your decision.
I also want to bring up the leaked sets point. Doesn't that also say that more people are buying those fansly sets if they are leaking, or the barrier of entry is just lower. There is a good amount of the patreon topless leaks, but not 100%, so maybe those people are more loyal, and want to keep that content exclusive, or there's just not that many people on that tier. In the end I think they (the models/cosplayers) are just covering all the bases, like for example samsung releasing phones in every price range. You might not go for the $1000 dollar phone, get the $300 one with less features, but samsung gets your money anyway, I think that's the business model. Lower entry point for the topless sets.