Ignoring for a moment how insecure most cheap locks are (including locks on safes), little safes are rarely effective vs a prybar + carrying them away to be cut into at the attacker's leisure. Larger safes have some of the same issues w.r.t. cutting, but you can make it less convenient for an adversary to do it (and make them spend more time where they might be caught).
The $50 safes are not fire-rated... and hardly break-in rated.
For fire-safety you need something big, and mostly heavy, which will be costly (shipping/moving it alone)
Break-ins are not in my threat model for a document safe. If they were, I'd get a deposit box at a bank. I just want some of my personal mementos and documents to survive a fire.
