I think there are other factors in play here. I own a steel boat (Amazon 44 pilothouse cutter) and it certainly wasn't cheap 1 year ago. But boats from unknown builders, or homebuilts from known-good plans implemented with unknown levels of skill, are definitely worth less and are much harder to sell than those with "comps" -- even if in good condition and well-outfitted. Insurance companies look a bit more closely, and savvy surveyors are harder to find.
Rust indeed never sleeps, though - sheesh! A ding through the Awlgrip thanks to a bobbing dinghy gudgeon took on a patina within a couple days, then heavy rust within a month. Ospho, Bag Balm, and Tie Coat primer have drifted to the top of the maintenance goo-bin.
Steve
S/V Nomadness