If you are set on getting this snake, and I can completely understand the urge to "save" it, I'd suggest first you have a very long chat with this so called reptile person. Since you went to school with him perhaps you can get him to see the light about proper care (feel free to direct him to this website).

Normally pet stores don't get in larger snakes like that, they tend to get in hatchlings so I suspect they got this one dumped on them and are trying to make a big profit. I'd ask them VERY directly where this snake came from and how they expect to sell any animal in such poor condition for way more than current market value. You may well have to spend money on vet costs if this snake is not well (sometimes acting quietly like that can be a sign of illness, not easy nature when it comes to adults in pet stores with no known history).

Buy it if you want, knowing you are supporting a bad place with your money, but I wouldn't give them that price and I would give them a piece of my mind.