(Video Link)
A company called Bottoms Up Beer designed a beer dispenser that fills up cups from the bottom. Presumably the dispenser opens and then closes a perforated hole in the bottom of the cup. Or it's magic.
via reddit | Company Website (warning: self-starting sound)
(and we never re-use cups--yuck!)
Since there is less head on the beer than from a traditional pour, it looks like more beer rather than less.
As for more money, this should save the vendor money by lowering labor expenses and increasing sales volume. But considering the captive markets in which these most likely will be deployed, I've got to admit that the savings probably won't be passed along to you and I.
Name one venue where you purchase a plastic cup of beer and you reuse that same cup for subsequent beers.