I rarely sell younger then 12 weeks, never before 8 weeks. In fact, in my state, it's illegal to sell puppies, kittens, rabbits, etc under 8 weeks of age. I do not keep a lot of rabbits (just 18 holes for the fuzzies right now and they are my main breed - 40 total holes, 2 for my ancient pet pairs, and the nephews and niece and hubby each have 4 holes they play with). We will be adding 4 more holes, probably for my fuzzies - lol.
When I do sell pets (which is rare), I charge $20. 8 weeks at youngest. If you are selling for zoo food, I do know someone that takes culls but he does not pay unless they are over 5 pounds (and then it's only $3).
( I do have a few "overflow" holes that will hang outside the barn, plus plans to make a bunny yard - not sure if I will colony raise meat rabbits for our own consumption or just to have for the kids to play with their bunnies, which is more likely because I have a squeamish husband whom won't even try rabbit meat - grr - frustrating!)