IMHO, $5k is well above the "used bullion safe" price.
Do you need a fancy interior? I don't. I got a used TL-15 for $350 (I had to move it out of the office it was in) and a used TL-30 for $500 (same deal as the TL-15). The TL-15 doesn't offer fire protection but my guns are insured. I bought a set of rifle rods, glued the felt to the bottom of one of the heavy steel shelves that came with the safe and filled it up. It's simple and not attractive, but it offers way more security than any regular "gun safe" and it cost less.
Oh, and mine is in my garage, unheated. I use rechargeable desiccant canisters. I added a silicone door seal to keep the dry air sealed in and I don't access it regularly.
I don't expect it to survive a fire but fire is less of a concern than methbillys coming while I'm at work.
ETA, I should have mentioned both safes are about 3,000 lbs. The TL-15 is a full 6 feet tall, 3 feet wide and 32" deep. The door was going to have to come off to fit in my house and I didn't care to move it in that way. We just used dad's forklift and set it in the garage.