Well, maybe - as long as the seller understands and agrees that the price is based on a clean survey and subject to renegotiation based on what the surveyor finds.
I view it differently. I did the survey first. I knew what the asking price was, becuase it was listed in the seller's ad (of course). So I knew where he was starting. The only question then was how far down from that he would go. I didn't want to start discussing that until I had the surveyor's report in hand. Even if I ended up walking away from the boat, I figured the couple hundred bucks I paid the surveyor would be worth not ending up with a boat that had more problems than I realized (which, come to think of it, I kinda sorta did anyhow, a little but) or ending up paying too much.
Worked out very well - the surveyor came back with a valuation $700 less than what the seller was asking, which made it much easier to make him a lower offer - which he accepted.
Sure, there are different schools of thought. I took it for granted, but probably should have mentioned, that of course the agreed price is subject to renegotiation, and the contract is subject to cancellation, if the survey reveals deficiencies.
As to surveying before having an agreed price... As a seller, I would not let someone survey our boat if there was no purchase contract in place. A survey is a day-long affair of crawling all over and through the boat, including haul-out and/or re-launch. I wouldn't permit that unless I knew the prospective purchaser was genuine. My solid reasons would be a contract to purchase at a mutually agreed price, and earnest money.
As a buyer, I would not go to the expense of a survey until I reached agreement with the seller on a purchase price. The survey contingency allows for price renegotiation or other concession if issues affecting the valuation of the boat are discovered, so there is no risk to me. I can renegotiate or even walk away from the purchase if I don't like what I find. But if I like what I find, I have already reached an agreement on price and there is no chance the cost and time of survey will be wasted.
I can see certain scenarios where someone might do things differently. For example, some buyers who are purchasing from a long distance sight-unseen, will hire a surveyor to essentially be their purchasing agent. In that case (i.e. in lieu of inspecting the vessel in person) it might make sense to get a complete survey before deciding whether to make an offer.