How much is a 12k gf bracelet worth if the bracelet weighs 78 oz?

Uh, for one, I don't know what kind of bracelet you mean, but that's a nearly impossible weight- That equates to nearly 5 pounds. I would assume you meant something like 78 grams perhaps, though that's still on a massively high side, as few chain necklaces are that heavy.

Also, 12k GF is gold filled, it has nearly no melt value and is only possibly worth anything as a piece itself; Ask someone who can see it for a more accurate value based on the piece itself.