Short answer: Yes, they sell if the price is right.
Longer answer: It's a lot of work to get them sold.
If your boyfriend is worried about money and this is your hobby, then as long as you are covering your portion of the household expenses (assuming you're living together), you should be paying all of the costs and collecting payments for the snakes. If you are not covering the household expenses then he has a legitimate concern, and if you're not living together and the snakes are all at your place and you are caring for them, then it's really none of his business as long as you're supporting yourself.