I think your art could definitely sell! Though on TBT, cash comms seem to be more an exception than a norm. I think there are a lot of younger members who might not be able to buy yet compared to somewhere like DA.
How long does it take you per piece, do you estimate? From what I've seen $10 is a reasonable base for chibis. People will always want a lower price of course, and if you're really fast then charging less ($5-8) might get you more sales, but you wanna make sure the payment is worth your time as well!
So I'd say $10 minimum for a full body chibi, personally. You might look around at what others are charging, and if you want to sell for BTB I'd recommend doing an auction to get a feel for those prices.

Your art is really cute! If you decide to sell pixel chibis like the ones on your DA, I'd definitely be interested in one.