Sounds about right. Also, this was an above-stove unit, limiting possible choices. Probably could have more easily found a standalone unit that worked.

Especially if it was an odd size. The downside to built-in microwaves is that it took many years for the industry to decide on what sizes they would support, so older installs are always a crapshoot. If you have a weird one it can be hell finding an appropriate microwave. My parents had a very old microwave (1980s era) built into their house that was much bigger than almost everything on the market today, finding a replacement for it was impossible, they ended up having to buy a smaller one and making a custom shim to fit it in the old cavity.