I have long been a self proclaimed treasure hunter. I love to get a good deal, as do many of you guys on here. I have often found that it can create a difficult situation when an item is priced higher than what we are comfortable spending or we think there is an opportunity to get a better deal. Any ad with O.B.O is a perfect example.
I have taken the following approach based on advice from a cousin of mine who has been a collector and dealer of antiques for decades.
When I find something I like, I decide whether I will buy it at the price listed. If not, then I am totally prepared to walk away and often do. We have all been to sales, shops, etc in which the prices are just unreasonably high.
If I will buy it at the offered price anyway, then I ask the following question. " Are you flexible on the price?" This is non-threatening and it doesn't put you in a position of offering a price too low and insulting the person. They will say yes or no. If they say no, I buy the item at the offered price. If they are flexible, then I just saved some bucks.
I find this approach very easy and it isn't as uncomfortable for buyer or seller. FWIW.