I recently bought a Mac mini M4 16 GB - mostly to run Immich. I assumed I needed a Linux box. After a lot of researched I was quite surprised that the mac was the cheapest option. So not always an Apple tax.
For Immich, the cheapest option will either be a NAS or a used laptop depending on the amount of data you need, I wouldn't buy a mac for that.
(I just run the defaults on my CPU, works for me)
I think the decision comes primarily on how much data you would like to store for Immich, if you want to go cheaply, a 100 bucks used laptop will do the job, if you have too much data, a NAS will be more suitable (and you are certainly not going to get a mac where you can plug multiple internal hard drives for the price of a NAS)
That needs to be in (v)ram for searches.
Apple has always been the most cost effective choice for the value you get going all the way back to the Apple II, it's just that the floor of that cost has always been high. Anyone who thinks otherwise is a just a fanboy one way or the other.