value of stuff

Simply put, they're worth what someone will pay you for them.

On those, the oxidation looks pretty heavy and the knock-out looks like it was cut with a hammer rather than a hole saw. Mickeys were made with decent aluminum though and usually clean up nicely. Most of the time you can get $50-$125 a pair in similar condition regardless if they're the Holley / Mickey Thompsons like yours or the more recent castings. Some M/Ts for the big blocks were made in Japan with inferior metal and minor cosmetic differences. They're easy to spot.