I suppose inflated asking prices are due in part because there is no system in place where brokers take known sale figures and advise the prospective seller what a good number would be if they want to sell their boat reasonably soon like they often do in real estate.
There's more to it than that.
You simply cannot establish a value for boats the way that you can for houses. Boats have no "land value" that exists independent of the value of the structure. Boats move around. In real estate location is key, and it is very unusual to find a $6-million mansion next door to a $6,000 mobile home. In a marina, this is actually pretty common.
Of course, condition matters with a home, just like with a boat, but only a very small percentage of boats have someone living in them, compared to homes. And when no one is "home" for months at a time, the condition of a boat can go downhill very quickly.
Beyond that, every broker I've ever chatted with has stories about owners who simply refuse to believe what the real value of their boat is, and demand that it be listed at an unrealistic price.
So a $20K repower may only be worth $5K to the lender, even right after work is completed. On older boats it may have no value at all.
True, but this is actually one way in which boats and homes are somewhat similar. Spend $20k creating an elegant outdoor barbecue area, or putting in built-in shelves and converting a bedroom into a library, and it is almost certain that you will not add $20k to the sales price you can get for your home. What you will actually add will depend to a large extent on the features that other homes in your neighborhood have. The point being, that some upgrades add a lot of value, and some add almost nothing. Some sellers think they should be able to recoup the full value of everything they've done to the boat or the house, and they end up over-pricing as a result.
If you have the cash, you can pay whatever you want.
That's always been true, but the real point here is that a boat is a disposable luxury item that can depreciate to be worth less than zero. And I do mean that quite literally. There are boats out there that cannot be given away, because the cost of disposing of them is going to be greater than any scrap value that can be recovered from them. This almost NEVER happens with real estate. As mentioned above, the land almost ALWAYS retains some value, even if the home itself is good for nothing but tearing down. And the reality is that real estate usually goes up in value over time while a boat almost NEVER does.
Because of this, you simply cannot expect to buy a boat the way you do a home. It's easy to get a 90% loan on a home. You can even get zero-down loans on homes sometimes. Or an interest-only loan. Try getting any of those things on a boat!
Good luck finding what you want. Really. But if you approach boat-buying with the idea that it is a lot like buying a house or a car, you are in for a lot of surprises--most of them probably unpleasant.