It would depend totally on the buyer. If you brought it into the PC shop I work at and it had no problems with picture quality or anything else, you could get a store credit for $35. If you found the right person you might be able to sell it for $50 or a little more.
Depends on the model. I wouldn't sell it for less than at least 50-70 bucks myself....especially when you consider it could probably wipe the floor with just about any 17" LCD if it is one of the nice flat trinitron AG screens. The deals on 21 inch+ CRT's are so unbelieveable these days though.....I mean just look on ebay. Truly a buyers market so to speak.