1) market was filled between 1970 and 1990...the used market cannibalized the new market, so that only victims of "footitis" (35 to 50) bought new boats.
2) recession and changing tastes killed a lot of builders, even the mighty C&C.
3) cost of production due to rising resin prices in the '80s trimmed profits and led *in some cases* to shoddier, skimpier lay-up schedules, which gave the perception in some model lines (Hunter, for instance) that the boats were poorly made or corner-cut too much.
4) demographics meant that the pre-Baby Boomers and Boomers who bought boats in their 30s and 40s weren't present in the post-Boomer period in great enough number to sustain the market. Now those original owners are 60s-70s (just look around any club) and are finally parting with those old '70s boats because they are swallowing the anchor or buying a trawler that is more geezer-friendly.
The demographic thing has benefited me twice now. I'm 45, which makes me a tail-end boomer or a greybeard Gen-Xer, depending on who you ask. My wife is 33 and there simply aren't very many people her age around. I bought my first boat, a 33-footer, in 1999 for $23,000, bargained down from $31,000. The previous owners, about five years older than me, bought it in 1985 for $38,000 and it sold for $40,000 in 1973(!). I got an estimate from a surveyor in December for insurance purposes, and after about $10,000 of repairs, replacements and upgrades (including portlight replacement, retabbing, deck core rehab, backing plates everywhere and a rebuilt engine), the boat is worth ...$20,000. I don't regret this, because it's a stronger, safer boat now. But as an investment, it stinks!
However, we just bought a 1988 41 foot custom steel pilothouse for $125,000. It needs about ten grand of electronics upgrades and ten grand of engine work and structural changes (a hatch cut, some weld jobs, and a shower stall built in). Not a big deal. But I bought it from a guy who bought it in 2002 intended to sail around the world...and didn't...and *he* bought it from the commissioning owner, who intended to sail around the world...and didn't, because he got too old. The boat is valued at $150,000, but would cost $350,000-$450,000 to replace, due to construction quality, materials, labour, etc.
Go figure that one out.
All this blather is meant to make you think that maybe a '90s boat isn't going to be a bargain, and that the market is very good for good, old 30 footers that around PHRF racers. There's a large segment of retirees with decent smaller cruisers from 1984 back (and 1984 is when some companies started to skimp) that need TLC and (frequently) electric redos and gate-valve thru-hull tear out and other modernizations, but it needn't be a huge job, and in many cases can be done in stages.
I've mentioned the great 1977 Pearson 30 a friend picked up last year for $10,000: at that price, new running rigging and sails, a new charger and AGM batteries were pretty much no-brainers...and now he's got a very nice lake cruiser capable of saltwater coastal cruising as well.