I'm a younger player(24) and while i didnt grow up in the "good ole' days" or what have you, i think the quality of todays fender's are quite good. Sure they don't have mojo or whatever, but the chance of getting a lemon is quite low. I've been playing since i was in high school and even in that time frame I've seen the Americans and Mexicans get better. The Mexican's in particular. They used to have crappy knobs, thin pickups and came in boring colors. Now they look and sound much better. When i was younger, i was in guitar center every day after school, week after week, year after year, playing fenders. Old used ones, new American ones, cheap Squiers. I felt like every year they got better and better.
Two of my uncles grew up in the 70's and 80s. They both play bass. Their consensus is that Fender along with Gibson, were putting out lots of dogs. Both Guitars and bases. It wasn't just the thick paint or weak pickups or the 3 bolt kneck. It was the horrible routing jobs, Ugly paint jobs(70s sunburst anyone...), crooked hardware, poor tuners(on the guitars), and lesser tone woods being used. They say they remember a big trend amound playings moving towards Imports, like peavy and other brands, because while taste in tone was changing(hi fi sound, new wave) people also felt they were getting better value for their money, even when paying for a cheap japanese instrument.
Now personally, most of my favorite actively performing bassists, such as Carlos Dengler, Peter Hook, or Tim Commerford, etc don't use vintage basses, and yet they have great tone.(Commerford recently even switched to Lakland) This leads me to think that the sonic "superiority" of older bases/guitars is a bit over rated. Sure they look cool, and if you want a funky broken in bass, two thousand bucks ain't bad, but don't kid your self into thinking that 70s basses in general are better than modern fenders or sadowsky's laklands, G&Ls etc etc.
I think market changes have made 70s more expensive. I think their popularity has been constant at least among the bassists i know. Some people love the big headstock, block inlays, binding, etc. No one i know thinks they sounded better, just looked better. But prices are going up, and i don't think many of those same people are willing to shell out just for those features when they can have a better playing/sounding reissue. Some people just want a reliced, beat up "old bass" and since 60s fenders are recockulously expensive, some people ignore the cognitive dissonance and forget CBS and glow over their "vintage" fenders"