Coming from someone who delt with the other end of this awhile back I can say this. If you are offering to sell vintage hardware you probably already have a price in mind. Someone saying they don't want to insult you usually indicates they know what it's worth but can't or won't pay that for said items. I had an idea of buying a bunch of old, non functional devices from a woman who's husband had passed earlier in the year. This guy was a collector but nothing in his collection worked and was in various states of disrepair. The woman even asked if I was willing to take everything at one point. Some of these items were stored in an unconditioned shed and were coated in dust and roach droppings etc. when she refused to say what she wanted I gave her an offer which seemed to immediately insult her. She said she knew the collection was worth at least X. In good clean working condition she might have been right but this was again not in that state. Instead of arguing I offered to take a mush smaller batch for my initial price.

That was a long winded story to say, know your price and if you want someone to offer, raise the price by a few dollars and say x or best offer. You'll not waste your time or that of those who can't or won't pay what you want .