Hit the PX section and you can snag top quality for budget prices. LaRue, Badger, and Nightforce mounts can be found in there for great prices. Sure, a lot of dudes will try to get full retail for their used stuff, but they end up dropping the price after a month of bumping and wondering why no one wants to pay $300 for their “like new” mount that retails new for $280.
If you need QD, then I’d try a LaRue. LaRue gets a lot of hate on here but I’ve never had an issue with their mounts on ARs. You can find them pretty cheap on here (around $120-$150 shipped).
If you don’t need QD, which no one really does, then check out Badger and NF.
The new search engine will help shift through the Accessories and Optics pages for some mounts, which is way easier than what it used to be.
Also...
Don’t buy shit rings/mounts that have to be lapped. Buy quality modern day mounts and you don’t have to worry about lapping. ....this isn’t the 1940s...