In a game I play on, it's somewhat commonplace to see adoptables being sold for $10+. I myself have paid $100+ for certain adoptables.
Does it sound silly? I suppose so. But then again, this is why; I love art. I absolutely adore seeing the characters that I have created into something that's tangible. I like seeing how the artists interpret my descriptions in their own way.
It's pretty much the equivalent of me going to, say, deviantart.com and then commissioning one of the high-quality artists there to make a picture of one of my characters. Do note though that all "pets" are all uniquely coloured and made so not one are the same (With the exception of twins and triplets. Yes, they breed too ^^).
It also helps when the artist is amazingly talented ;)
I also run some where people are willing to pay $15 a piece. In this particular occasion, I get a lot of requests from people to dedicate the adoptables to passed on family members, friends, and even pets. There are also people who want to create their own persona in animal form.
I guess overall, it just depends on how you look at things :)
Oh, and here is an example of what people pay money for (I got mine with a custom pose as a staff member).
Lupinus (Anthro form of the Lupines)
Examples of lupines themselves (Yes, these two are cosplays XD );
