I don't like bartering for goods, not because it feels cheap on my part, but because it speaks of default greed on their part. If they have room to negotiate on price, then they're asking for more money than is fair, before I even arrived. Either you're running a ripoff business or you have no room to negotiate on price. The guy coming to fix Dad's ceiling after the storm lowered his price four thousand dollars in one hit, because the insurance company asked him to. Four thousand without blinking an eye. To me, that says "do not do business with this man at any price".
Mokalus of Borg
PS - That's just my opinion.
PPS - And the roof guy is an unusual example, I think.