Okay I can buy at preev +5 only.My logic is simple,if you sell at any exchange,you wont get more than +5 preev so sell it to me at the rate that you would sell to exchange.
If I have to buy more than that,why would I buy with any individual,better I buy at exchange.
In short give me a better deal than exchange
People don't buy with exchange because its easier to trust a person than a corporation. An individual that is trusted by the community is a person and not an inanimate corporate entity. People associate emotions with an individual. Hence your payments details with an individual is safer than it is with a corporation.
So you are already getting a better deal than the exchanges. Dealing with an individual, the extra % is basically the worth of your privacy.
So please, don't be offended if someone asks you for better percentages than +5% preev. Just my 2 rupees worth of opinion.