Selfishness and egocentricity are not the same. An egocentric person is one who (in part) is unable to fully understand or to cope with other people's opinions. Mongo thinks people who buy vintage instruments are foolish because he doesn't see intrinsic value/attraction in them. No different than me stating you are foolish if you like mayonnaise just because I can't stand it.
Is anyone who buys Levis over wallmart Wranglers foolish? The objective quality in the two is the same, and the Levis are not inherently better than the Wranglers; the Wranglers are certainly cheaper. I'm sure you could come up with example after example of this sort of thing. People don't consume strictly based on utilitarian reasoning and usefulness -- this is not limited to the vintage guitar market. Frankly I'm a bit shocked so many people are having trouble with this.
e·go·cen·tric
ˌēgōˈsentrik/
adjective
adjective: egocentric; adjective: ego-centric
1.
thinking only of oneself, without regard for the feelings or desires of others; self-centered.
"their egocentric tendency to think of themselves as invulnerable"
synonyms: self-centered, egomaniacal, egoistic, egotistic, self-interested, selfish, self-seeking, self-absorbed, narcissistic, vain, self-important
Definitions might help you relieve some of your shock. Also, with regards to Levis vs Wranger - I would not be surprised if both are made in the same factory in Asia. So yes, if someone pays more for the same thing they are exceptionally foolish. But you proved my point - if the Wranglers are cheaper and the quality is the same, then someone who pays just for a label is a knucklehead.
All I can gather from mongo's posts is that he recognizes the verifiable fact that vintage basses are only universally superior in price. Sound, feel, etc. supercede age and model. Many people think with all their might that Pre-CBS Fenders inherently sound better. Less, but still many, also think those in the 15 years afterward sound better.
But there's nothing about Pre-CBS that makes them any better other than subjective opinion. A blind test would be factual evidence that no one would be able to tell the difference between models spread across the spectrum of age and quality with regards to Fender. But of course, those tests would be dismissed.