"So how does some guy charge $500 to come poke at a boat? Not happening. It's worth $100. "
Sounds like you've always been an employee and never self-employed.
Let's say the surveyor takes two hours on your boat, and spends another two hours in travel time, coming and going. So you want to pay them $100, which breaks out to $25/hour for the job.
Except, someone who is self-employed and running a business actually nets only about 1/3 of their billable rate, after accounting for vacation time, pension, sick time, and both halves of the social security (FICA) taxes. Someone who is real good at it, might net half of their billing rate.
And you're going to pay them a whopping net $12 per hour then, and expect them to eat the costs of gas and car mileage as part of that? Hell, they can make more than that supervising the fryer at any burger joint.
You won't find a plumber or an appliance repairman to come make a housecall for $100, why should a surveyor charge less?
Some boaters can do better for themselves than what some alleged surveyors would do, sure. And if you buy a $5000 boat that has a couple of surprises, and you sink in another three or four thousand (don't forget the rent on the ground or slip under it while you're working) and then you first find out, it can't be fixed or other folks don't want to buy it and the landfill won't take it because it is classed as hazmat, ka-ching go to the hazmat disposal site...
You might decide the surveyor, like those other guys, wasn't totally unreasonable after all.
But either way, someone needs to get some face time UNDER the boat, to see if there are problems with the keel or rudder. And with the rudder, if there is even a hairline crack in the paint, that can mean water intrusion and armature failure to come. So you really want to take a close look, hauled or not hauled.