If there aren't enough people on the platform it might be a waste of time for startups, and if there aren't enough valuable microstartups it might be a waste of a small fee for prospective buyers, but expensive it isn't...
If it is valuable, $25k seems low. But then again maybe at that point it's no longer micro. But who would be looking to buy before there is substantial success?
There's a million and one ways of doing things, the way patents work is a specific implementation.
Gaining a patent amounts to throwing stones at each other.
20k is a lot less than hiring a HR department and finding a developer. Haven't looked at the site, but was assuming some of the ideas have an MVP of some sorts.
Without any sort of preview or proof of value, it seems like quite a steep entrance fee to spend on potentially seeing some interesting IP to acquire.