I've bought and sold a few boats, and looked at a lot more! A few points...
Most sellers ask a price that they would accept straight away, they expect to have sellers haggle. Also buyers expect to be able to knock a seller down and feel better for it! As an example, I bought a house recently, as it was exactly what we wanted I offered the asking price for a quick sale. Bought the house ok, but the owner wanted to haggle over £20 for some fittings.... realistically I could probably bought the house for £6k less if I'd been prepared to wait.
Some buyers have to travel a long way, drove 700 miles to look at my last boat and 850 for the one before that, it's a big investment especially for the cheaper boats that I can afford. I drove 1500 miles to look at a P22 some years ago and walked away from it, didn't even make an offer as it was not really as described.
I think it's only fair to agree a price in principle with a prospective buyer before a viewing if he wants to do that, with as much accurate information supplied as possible to enable him to make an informed choice. Serious buyers know what to expect, know what it's worth and if they're taking the trouble to come and look at it then they're pretty serious about buying. If I thought a boat was overpriced and the seller would only discuss the price after viewing then I wouldn't look at it unless it was local.
"I'm not lost, I'm exploring...."