An uncle of mine (a successful small businessman) used to preach “Don’t do business with a friend unless you’d be happy to do without the money and the friend involved in the future.”

That’s a bit harsh, but there is an important point to it.

Like in the scenarios here, if you offer something for sale to a friend or acquaintance, there is often the unspoken assumption that of course he will realize that you are offering an excellent price for his benefit, and he should be appreciative of your generosity.

If the friend does not seem to share that view of your offer, it’s easy to feel offended, and in contrast to dealing with a potential customer who is a stranger, any reaction may be trickier.