What size? Little ones (<6") tend to be pretty cheap; I've found them in the $10-20 range. Slightly larger ones tend to be a little more, and big ones can be hit or miss for pricing. That's just from what I've noticed around me and online, though; it all depends where you are in many cases.
It also helps to be in a legal state considering that they could put you in the negatives if you acquire them in a state that has a ban on them and get caught.
