How Important is ECC Memory?

Hello fellow selfhoster, I was wondering how important it is to have ECC Memory. I want a server that is really reliable and ECC memory pops up as one of the must haves for reliability. But it seems to me in my research that it is quite expensive to get a setup with ECC memory. How important is ECC memory for a server (I rely on).

So far I have been rocking a Raspberry pi 4 which has ECC memory