HRE Wheels are super high quality, but there's a point of diminishing returns over something like Aspira, BC Forged, Signature, Rays, Advan etc. $4-5k for a set of quality forged wheels can be justified, especially when you consider the strength to weight ratio, craftsmanship, and quality of the powder coating. However, $15k is simply absurd. There is a marginal difference that one could barely tell when jumping to HRE. You'd most likely have to have the wheel next to another set of high quality forged wheels to really be able to pick out the differences. Part of the reason why they're so expensive is the amount of rigorous testing they go through to get all those approvals from various standards.
HRE wheels are usually found on uber high-end show specific cars, but you can see a few people running them on their dailies. Who am I to judge, though? Go for what you can afford and like. HRE wheels do hit a elite tier.