Double Naught Spy
Sus Venator
Always ask with this magic phrase "can you do any better on the price?" It is not offensive.
It may not be directly offensive, but it is a sign that you want a better price and are not willing to put forth any effort to negotiate. It is not a good way to truly get a best price. You are a lot better off making a cash offer for the item instead of a backhanded insult of asking for a better price without offering something first. The price tag is the offer to sell. If you don't want to pay the asking price, then make a counter offer.