Bare minimum, let's take the US minimum wage and apply that to the work needed for an existing model then. assuming it already had bones, visemes, and blendshapes already there- it's very likely that they had spent more than a day or two worth of time ensuring all the bells and whistles work, the visuals plays nicely with VRC, the rigging works in fullbody, small things like the radial menu being organized for customers are all good- the list goes on man. 

Anyways, I guarantee the model did not end up in its finished state within ~8 and a half hours which is the equivalent of $60 for the lowest possible min. wage in the US. I'd say paying proportionally to a fraction of the time spent on the model for the finished product is pretty well worth it. Most pre set-up avatars these days are around that range anyway.

People shouldn't complain about the price of a luxury item, especially for one that has a model available for free. If it's such a big deal they should just go and implement all these functions themselves, unless we're gonna realize that the skills and polish needed for stuff like this takes time, and a lot of it, and time is money. I think anyone who's fought with unity and blender before will know.