The boats are easy to buy, keeping them- the who and the where, that seems to be the dwindling commodity. Plus the cost to refurbish the neglected ones and keep the good ones in good condition, is rising. A T-30 is a good indicator, a well built popular boat, but even the sought after highest end boats in their 40's are taking a hit. As you suggest, and I agree, the soft market brings all values down in these older boats, no matter the boats popularity. A lot of boats will become a negative value this year, joining a growing group. In some ways, it reminds me of the housing market.
My boat is 51 years old and lost 10% value in the last 10 years according to a value survey. As I've restored it in the last 10 years,... that's embarrassing.
For the market overall, it's discouraging if you're in the production(even semi) boat boating business. What sort of boats do you build, and why? It doesn't effect those of us that sail in affordable boats in affordable areas, I wonder about the rest of the industry though. Maybe this is a big correction in the sailing industry, now ongoing.