I like kicking around boat yards and checking out boats, because that is the kinda guy i am. I can fumble my way through most boat systems and can likely figure out what i need to know- but as hard as it is to believe, not everyone is like me.
So, if you don't like that sorta stuff, if you are a clean hands sailor, (lots of them out there- it is why yards stay in business) how good is your self-survey going to be, and how much do you NOT want to do it?
Your point is very important.
Another thing that hasn't been mentioned before is that even very experienced professionals can make poor decisions on their own potential boat they would never make on a customers boat.
If fact due to their experience it may be easier for them to underestimate costs.
I have seen pro's fall in love with a boat because of the pedigree, lines, low price etc and convince themselves they can rectify all the faults quickly and cheaply.
If it was a clients boat they would have given an accurate appraisal of the costs and condition.
But because it was their own dream they were particularly convincing and capable of fooling themselves.
There is something about your own potential boat that makes otherwise level headed guys go all gooey.