I worked in contract manufacturing for making electronics.

We had certain contractual yields required. If the yield was below 90% (industry standard), they would pay us for the scrap. The assumption for that being they should have a confidence and reliability in their process that allows it to be higher. If we produced a higher yield than 90%, they got those for free.

Of course, yield numbers and reimbursement terms can be negotiated as part of the contracts.