Listed from most important to least important of those things I think of when buying a snake:
HEALTH OF ANIMAL
CB vs WC
EASE OF TRANSACTION (which I think includes the attitude of the seller)
APPEARANCE OF ANIMAL
PRICE
POTENTIAL FOR PROFIT
Health will always, forever and ever, be the deciding factor of whether I will or won't buy a snake. I recently was looking at a snake and it was a beautiful snake, priced right for the morph, but it was older than I would normally accept and it has just produced slugs and only slugs.
I don't think I would ever buy a wild caught animal, but I guess if it was healthy and it would make a good addition to my collection I would consider it.
"Ease of transaction" and "Appearance of animal" could be swapped, depending on why I'm buying the animal, for beauty or for genetics. I will put up with tons of crap in the transation if I end up with a beautiful snake in the end, but when I'm buying for solely the genetics that a certain snake has (e.g. het for something) I really don't care how butt ugly it is as long as I know I won't have a hassle with the transaction.
Price is obviously important and initially that's the main thing I think of, but it eventually gets pushed down to this importance because the other things are more important in the long run of the transaction.
Profit if also always on my mind when I make a buy, but it never gets very high on my priorities. After all we are in this hobby for the fun of it not the money, right? 
I may change my view on the importance of these things for future transations, but this is what I think right now.