We bought our 1999 30' Airstream Classic in 2005 for $22k. Over 15 years we've done multiple upgrades (carpeting, upholstery, hydraulic disc brakes, 16" wheels, and all new appliances etc). Probably have invested $10k in upgrades and $5k-$7k in regular maintenance (plus $200/mo covered locked storage).
That's the background. Knowing values have gone up, I got a certified appraisal to make sure my insurance was sufficient. Value came back at $42.3k! So, we actually made money on this 'investment' if we wanted to sell into this hyper environment.
Coming in to retirement we considered getting a new one, but the $165k cost and reputation for disastrous quality control, particularly on the new high-tech stuff, just didn't make sense. Instead we'll probably put $10k into renewals of carpeting and upholstery and upgrade to 50 amp and dual A/C.
In 3 years, I predict that used entry-level RVs will flood the market as people realize they don't use them much, they require a certain mechanical aptitude, and most desirable campsites are overcrowded.
Might be a similar environment with boats? I don't know.