Hey Lars,
Can ya get a pic of it? I would be a bit iffy too, I mean, if it is a red tail, I have never seen one go for what he says they go for... unless it had some "special genetic" blendBut even then, I would still be iffy...... just b/c its in a pet shop. Does it look like the red tails you have seen pics of here? Or is it different? Can you find a pic elsewhere that resembles to show us? Another thing too, have you handled it? Have you seen it handled? I would be worried about its temperment.
Does it look like this:
http://www.boa-constrictors.com/com/...brasilien.html
http://www.vpi.com/5vpibreeders/SABo...onstrictor.htm
Here is a great resource too:
http://www.ball-pythons.net/modules...._content&eid=4