I spent about $1200 on my safe counting delivery and I think it's actually minimal for my needs. I don't have the opportunity to bolt it down where I live because I'm renting now. When I get to move back to my house it will become more secure. Mine is a "48 gun" safe although getting that many guns inside would be a real trick. They overstate the capacity of all the RSC's I've seen on the market. I'd say a more realistic number would be the 36 guns that you mentioned. So if you actually want to store 36 guns you'll need a safe that is rated to hold more guns than 36. That's just the games they play.
I didn't get one of the cheapest safes I could find but I definitely didn't go with a true safe either. I tried to balance the value of my gun collection with the value of the safe. I got a good price on the safe I bought and finding one at the price I got may not be easy in the post panic world.
No RSC is going to stop a determined thief either BTW. There are ways of slowing down the bad guys but if you're not home and they want your stuff they can get it even if you are bolted down and hidden plus having a wall built around your safe.
There are certainly advantages to owning a RSC of any type. Insurance companies would have to see that you were attempting to prevent theft for example. And it's going to be very hard for curious neighborhood kids to get at your guns preventing most tragic accidents caused by kids
There should be some formula to calculate how much to spend on your safe based on how much money you have tied up in your guns and other valuables. But I don't know of one.
One other thing. A garage can be a bad place to store guns and ammo. A cold spell followed by a quick warn front will mean a safe that sweats like
Butterbean on a treadmill. If your seal is good you probably won't have terrible problems inside but not all seals are good. You could open the door and find a puddle a few inches deep inside. A powered humidifier is a must in a garage setting and get the biggest one that will fit in your safe. They don't cost much.
What I have is a Fatboy Jr.. I have been very happy with it and like you I chose to get a non-electronic lock. There's a lot less to go wrong with a mechanical lock. I'd suggest doing lots of homework and listening to the experts on this board. They know what they're talking about. There are a few guys here who are experts.
Something I've been thinking about is the Liberty SafElert Gun Safe Alarm which monitors humidity and temperature and connects to your home wi-fi system to give you a warning that something is wrong with your safe setup or someone is trying to rob you. It works on batteries so the power line can't be cut except to the entire house of course. I don't know how well they work but I'd like to know.