People tend to overvalue what they're selling and undervalue what they're buying. Human nature. Good brokers try to reign their client in. If a boat takes years to sell, the market has spoken and said, "It's overpriced." If it's not being offered in the right market something is wrong. Certainly in five years one would try different ways or different brokers. So basically it ends up maintaining a price above market. That doesn't mean one might not get it in year 6 or 7 or 8, although unlikely. But the costs incurred over that time offset any price gain. I see people sell something quickly and then think they priced too low. More likely they just priced right.
The other aspect is someone prices well above what they're willing to take. No one contacts them. They think "Well, I would have come down, but I knew people want to negotiate." The problem is people search, look, qualify, get interested based on price. So you need to at least price within a reasonable range of what you would take. You price a boat at $420,000 when you're willing to take $400,000 you have a chance. But you price at $460,000 when you'd really take $380,000 and your potential buyer will never even contact anyone. They're probably saying to themselves, "I'll pay $350,000, but no more than $400,000" or perhaps even, "Want to spend around $400,000, no more than $450,000". You're just excluded from their search.