Beer is around $2.50up. I've never made it much past 2am and have been able to get a drink till then. I'm not sure what the official closing time is, but it is late. They also have specials where you can get 6 beers for the price of 5 or 5 for the price of 4. They do add 15% gratuity to your bar bill, this includes sodas.
I seem to recall draft beer on RCI going for less than a can or bottle of beer. I think it was somewhere around $3 for a mug, not including the 15% tip. I am pretty sure a can or bottle of domestic beer is $3.50 (or $4.01 after the tip is included).