Advice on Messed up Bulk

My manufacturer messed up a bulk order of around 20 something pieces, which I spent $500 on.
I’m trying to figure out what to do, and they offered to remake the bulk for 50% off the original cost, but I don’t think I should be paying for it since they messed it up and they were irresponsible.
What should I do about this situation and what should I do about the leftover bulk order that is messed up?