Please note that burrs will become dull after some hundreds of kg of coffee. But that’s okay, they are made to be replaceable and there are companies selling high quality replacement burrs.

We have an older version of this (so take this with a grain of salt, maybe the fixed some of the problems):

https://madebyknock.com/products/aergrind

And I can’t reccommend it. Grinding fine coffee is very hard and exhausting and the bottom bit is not screwed on but has some kind of mechanism that makes that part always almost fall of when grinding. Thanks to it being round and metal it would also be very hard to hold tight without slipping when the plastic ring around it at some point breaks. Would not but again but we have it and I’ll keep using it.

At that price point, you’re probably looking at a Chinese hand grinder. The good news is that these are actually really solid products. I have a hand grinder from Timemore that I’m more than happy with, and have been using for 4+ years without issues.

For espresso or drip?

The only espresso grinders < $100 are probably going to be used or maybe Baratza brand. Baratza does sell many of the replacement parts online, but occasionally the designs get updated and older models can be hard to repair without having to change lots of internals. The models share a lot of their internal designs however and they are quite durable.

Hario makes some good simple hand grinders that you can get new burrs for. The skerton model can screw onto a mason / ball wide mouth jar if you break the glass canister.

There are plenty of good higher end grinders. I had a Rancilio Rocky that I got second hand, made in 1985, used multiple times daily for years and only needed a small repair to the Doser lever spring. I changed the burrs a couple of times and gave it to a friend and it’s still running perfectly as a 40 year old workhorse. Not fancy but quite solid. The only real weak point is some plastics on the case, but they sell replacements. The designs have been fairly maintained over the years and parts are available. I’m pretty sure that if I bought a new Rocky it would outlive me today.

I picked up a handheld burr grinder maybe 20 years ago. Not even sure what I spent but I’m pretty sure it was under $50, no apparent brand.

find a good hand grinder. nothing really to go wrong on them especially if you get a sturdy metal one. ive had plastic ones break when dropped. still works fine tho.

Um it’s difficult at that price level, but monitor craigslist for a used Bunn G series. $100 is unlikely though. If you’re caffeinating multiple people with it, you might grind 100lb of coffee a year at $10+/lb, so $300 up front for a grinder spreads out quickly.