Obviously the Cheers! program makes money for Carnival, or they wouldn't have it. I would guess that there are way more people who don't reach break even than meet the maximum available each day. I also doubt that Carnival will change the price of most drinks to just over $20, or fewer people will want Cheers, which would in the end cost them, customers and money. I think they'll probably change things so adding premium alcohol where it doesn't matter (ex. fruity drinks just to "get your money's worth") will make it just over $20, but they'll continue to have most drinks (including alchemy) below the threshold.