Well it's this whole, "If it's old than it must be better or worth more" mentality, and the older the better as far as vintage value is concerned.
I'm not knocking this bass. It's in superb condition and even 70's stuff is getting harder to find, but I have a hard time justifying $6000 for any bass, and if I were absolutely forced to then it would be an Alembic, Fodera, or something handmade. But an assembly line bass? How much mojo or "magic" could it have beyond any other assembly line Fender? And even if it was special, is that really worth $4000-5000 more? 20 years ago you couldn't give 70's basses away and there was the whole pre-CBS vs. CBS argument. Fender's 70's era stuff was spotty quality at best (as was the case with many manufacturers then, ie. Gibson, Martin, etc.). Sure, you could find many diamonds in the rough, but you really had to look. Now EVERYTHING'S got value, even those garbage Musicmasters, which are inferior to just about any Korean bass made today and going for well over $1000, just because. What urks me even more is the greedy dealers who are jacking up lefty prices lately are the same greedy dealers who normally want nothing to do with carrying lefties, even though some vintage lefties can command 50% more on the market than a righty counterpart. So they help contribute to the rarity of instruments by not making them available to us, then when they finally get one they drive pricing up to insane amounts with the attitude, "Well, where you gonna find another?" So we get screwed coming and going.
I own several basses that have now jumped in value in leaps and bounds. To be perfectly honest, the whole thing makes me nervous. I still play my '72 J every day as my main bass, and I really don't want to start thinking about how much I'm depreciating it by playing it or have to consider retiring it for the same reason.