Thought this was an interesting question, was surprized at the result.
Assuming 3 meal a days * 365 days/year * 9,500 premium class seats in the main line UA fleet (varies from 8 to 64 seats)== >10M meals a year. (this is assuming 100% occupancy -- so may be a few percentage points high)

So if one assumes 33% overstock and meal cost $8-$10, we are talking >$25M. You can use you own overstock and meal cost numbers -- but this appears to be a non-trivial cost. On a per premium cabin passenger basis it is $3-$4.

There are a number of assumptions in the above numbers but it does show an order of magnitude impact.

CO just cut economy snacks for 1/10 the above costs.