Sound quality and fit/comfort vary
enormously among IEMs, and as Herb points out, the price you pay is not a reliable predictor. I've had several over the years, some of which refused to stay in place, some sat comfortably for hours. My favorites were from Shure (the since-discontinued SE-210s), which offered a reasonable compromise between comfort and sound quality.
The biggest problem with IEMs is reliability. Those itty-bitty wires break easily. Those itty-bitty drivers don't handle shock well. Some are prone to getting jammed up with impacted earwax than cannot be easily removed without damaging the driver. I just got tired of replacing them every year, so now I use some cheap Sennheisers, for air travel. They were like 30 bucks, so I won't cry when they inevitably break.
On the off-topic of airplane usage, I actually did A/B tests on a long flight to Tokyo. I'd borrowed a pair of Bose noise-cancelling headphones in addition to my two closed-back studio headphones and two IEMs. They all did a decent job of filtering out high-frequency noise, but only the Shure IEMs did anything for the steady low-frequency roar of jet engines. I was especially disappointed with the Bose, which acted more like a low-pass filter than a noise-stopper. In a non-noisy environment (in a hammock under a mango tree), they were quite mediocre-sounding. Not awful, but given their price point I'm sticking with my "ripoff" assessment.
But this is off-topic: due to their percussive nature, drums are actually harder to attenuate than jet engines.
BTW, I did an experiment once using the Shure IEMs with OSHA-approved ear protectors over them. The kind you see the ground crew wearing at the airport. They're too clumsy to wear while playing drums, but wow, talk about isolation!