^^ The problem is not whether or not some people should be spending (a lot of) money in order to get minimal improvements in SQ or not. It's been said already (several times) that there are indeed people who are aware of the 'law of diminishing returns' as you go up the ladder and some of these people will be willing to spend their money for such small SQ differences.
However, when I say overrated, I'm talking about different aspects that are often hyped/exaggerated, the most common of which - and possibly the most important - is the significant improvements in SQ. Many people, when they start researching for a new set of customs, look at customs threads. These threads are often full of hype and exaggeration, particularly the first 20-50 pages. It is usually many pages into a thread that you get a clearer picture re SQ, fit, isolation, re-fits, ear impressions, AND you also begin to hear quite a few horror stories re re-fits, and (very) poor customer service.
Unsuspecting/inexperienced new - and some not so new - members, often young, believe a lot of the hype and are NOT aware of the often minimal improvements in SQ, comfort, isolation and possible (extra) shipping costs. Some of these people, when noticing that they didn't get the SQ improvement they expcted, often start asking questions about getting new sources, portable amps & DACs, aftermarket cables, etc. These same people are also often told that they now need to listen exclusively to FLAC files or other lossless formats, when in actual fact a lot of these suggestions often offer no improvement whatsoever, or the differences are so subtle that most people would not notice them.
So, I'm not saying customs should not be purchased by anybody, but that I think they are not really worth it for a lot of people.
There is also an often ignored psychological aspect, particularly when talking about expensive customs - the need to rationalise/justify an expensive purchase, ie I have to convince myself somehow that the huge amount(s) of money I've spent is really worth it.
Like I said, $300+ on a set of universal IEMs is already (a hell of) a lot of money. This is not a problem for those whose hobby is/has been audio gear and have enough money to spend. Unfortunately, a lot of people are not into this so-called (expensive) hobby, and originally only come to HF - the most popular website on the web - looking for better earphones than their stock MP3 player earphones. A few months down the line, some of these people end up getting customs, amps/DACs, aftermarket cables, new sources, etc.
Yes, I'm aware people are free to spend their money the way they see fit, but I'm quite convinced that quite a few of people who have spent a lot of money in these products, if given the choice, they'd do things very differently.
True, also, that only trying out things for yourself is the best way to find out whether this is all hype or not. But, sometimes the price to pay for just testing/trying out new gear, as is the case with (expensive) customs, can be pretty high.
