The usual justification for professional IEM is hearing protection. It's often loud on stage.
There is a danger with headphones that you will turn them up too loud (esp. in a loud environment) so you can hear the signal clearly. As a musical professional your hearing is vital to the quality of your performance so you should protect it.
You can get custom made concert earplugs, they run ~$200 and are absolutely worth it if you go to a lot of concerts. I see 75+ shows a year and it pays for itself very quickly.
You can go to an audiologist or look into ACS[0] (who will take your molds for free if you're in NYC).
I'm skeptical of anyone who claims they have zero effect on the music, but the reality is they are quite unobtrusive and the manipulation is minimal. I find they reduce the fuzziness and reverb of shows, whether that sound is intentional by the artist or not, leading to a crisper sound (again, sometimes maybe to the slight detriment of the experience). If a concert is very loud they will greatly improve your enjoyment of the music. If you see concerts regularly, do it yesterday.
Check out Etymotic Research--they make all kinds of high-end auditory systems, including earplugs[1]. I've been very happy with their Ety-Plugs and also have a set of their ER20XS's [1].
They're relatively inexpensive ($16-25 USD) and work like a charm. They're amazing at reducing the volume very evenly across the frequency range without distorting the sound quality or balance, useful for everyone not just professional performers. You can hold a normal conversation in a really loud environment without screaming, they're great.
Yes, your local audiologist probably have them. These are mostly targeted at professional musicians. Mine were about 150€, mold included.
They usually have options regarding the level of attenuation you need, the ones with the highest attenuation tend to have the highest level of distorsion, but in all cases, it is way better than standard earplugs.
I also tried standard sized filtered earplugs (about $20) but without much success. Maybe my ear canals are weird but I couldn't get them to fit properly, so the sound mostly went around the filter, not through it, making them essentially useless in addition to being uncomfortable and not holding well. So if you are like me, save your $20 and get custom molded ones.
A friend put together a group buy of these at least a decade ago and mine are still doing great. They’ve gotten completely disgusting but some isopropyl followed by a warm water wash cleaned them right up. It’s kind of weird that such a relatively niche product is so cheap… I am so happy with them that I would be a repeat customer but the best I can do is promote them a bit since I’ve got no reason to send them another $20 yet.
There is a danger with headphones that you will turn them up too loud (esp. in a loud environment) so you can hear the signal clearly. As a musical professional your hearing is vital to the quality of your performance so you should protect it.