Lots of FFP scopes under 500$ now.
I got into it with the BSA mil mil scopes built in the same factory as primary arms.
That particular erector assembly is very popular for the lower cost FFP scopes.
I personally would probably go with one of them if I was going for a under 500$ optic. Just because it's been proven to track and handle recoil. I'm not saying the others won't, but they haven't been out as long as that style of scope. I would probably go with a Athlon Argos 6-24 because of the reticle. It's not necessarily the brand because there are several companies branding that scope, just with different reticles.