PROPERLY maintaining a boat is far more expensive than you may expect. I'm not talking oil changes and drive fluid checks. I'm talking recommended service intervals for valve springs, full drive rebuilds... etc. I suppose it's the preventative maintenance that is sometimes insane. Seems like there are two groups of thought on this. There are the hammerheads that go run the dog scrap out of their boat and won't turn a bolt until something breaks in half. The other group does every maintenance item by line when it's called for. I think that a large performance boat is much like staying on top of a house. You have to stay on top of maintenance and improvements or things can get away from you and deteriorate fast.
An old friend of mine that was in the rental property business would tell me that the best indicator of a tenant was the condition of the car they drove. He said 99 times out of a 100 if their perspective tenants car was dirty, full of trash with bald tires they were getting ready to trash your property and leave you with a few months rent. Those that cared for their vehicles, no matter what year or tier were the best tenants. I think this thought process can be useful when buying a private party boat. Look beyond the cosmetic condition of the boat... the owners lifestyle and other possessions could potentially shed a bit of light on how the boat may have been cared for.
Just my 2 cents... I'm sure some will disagree.