I'm guessing the "additional financial burden" is having to actually give people what you're saying you are, which means you can't save money by skimping on beer. You could save a ton of money by giving people one less ounce. It's actually a common business practice. For example, I remember listening to the owner of an olive bottling company talk about his idea that if you remove just one olive from each jar, it wouldn't really affect the consumer, but it would save the company a lot of money. (To be fair though, I don't think he was suggesting that the same weight by volume labeled on the bottle remain the same.)
As far as the "regulatory burden", I don't see what that would be.
Also, Paul LePage is a weird man, so that just might explain it all.