I also agree with the above said. If a gig description clearly states that " you get this for this much" and the buyer just specifically wants that, there are no issues at all. I have gone through more than 100 order cancellations throughout 2013 to today because of some buyers ordering before discussing and later cancelling the order telling that the actual cost was too much after i had explained.lol.
After all, what person goes to a shop and blindly purchases some random stuff, hoping that those would fit into the buidget at the check out!? i would categorize the buyers who discuss prior ordering as the light side. and the ones who doesnt as the dark side.