25 identical small packages is hardly "major volume". Since the APC is capable of printing stamps in an denomination, there's no excuse for omitting such an obvious function as "print N more like this one". Knowing the USPS, there's probably some silly regulation involved.
Yes, there is another "payment practice" I could have used: taking time off to stand in line during office hours at Christmas.
Then don't concentrate your mailing at Christmas. I don't.