They are gold plated so I doubt much gold on each card so it depends on how many cards you have.

I remember years ago the Western Electric installers would cut the tips off wire spring relays for the same reason. I don't remember how many, but I know it was a lot to get one ounce, as in many pounds of the flat contact tips. You're talking a very small piece of material so it probably took hundreds if not thousands of relays to get the require amount.

Retired phone dude