Well the thing is, not everybody can just jump in to get custom IEMs.
You need to pay extra and go through hassles to get impressions (and not everybody in the world can get impressions easily for reasonable prices, and reasonable shipping costs to JH). Contact JH, then sent to JH, wait, try on, and if they don't fit nicely it's re-doing that all again for time and money.
Another thing is the risk in terms of resale value. Universal IEMs are much easier to sell, while customs you probably will lose much more in case you end up unlucky where you just can't get a good fit (and yes I've seen unlucky people ending up selling customs for way, way less than what was paid).
They're simply not easy and assured as universal IEMs. And when it comes to universals, the SE535 is one of the best. In that sense, buying SE535 is not a waste of $400.
People who go to customs are pure audiophiles in my view, I'm sure you get better sound out of them but it's a trade off between the extra costs, hassles, risk and resale value. Although I may get customs eventually, at the moment I feel the SE535 and my portable rig is way more than enough for sound quality when listening outside, while walking or travelling. No time to concentrate enough in music. For crisp clear detail and soundstage I just use the T1 at home..