30 packs of High Life for $13 is about as cheap as you can get while remaining drinkable. The larger the package, the better. Don't waste money on 12 or 18 packs. High Life is a bit cheaper than PBR or Old Style, which are negligibly better, and Bud is more expensive for 24 cans. I can drink some cheap ass beer, but I won't dip into Icehouse/Keystone territory. I don't think there's a substantial difference in quality of mass produced lagers once you get over that threshold.
Another way to get more mileage out of cheap beer is to add a shot of some cheap whiskey, about half a shot per can. It improves the flavor and cuts down on the number of beers you need to drink (and the amount of calories taken in).
I wish Steel Reserve came in larger quantities, but I can get pretty drunk on 2 24 oz cans for less than $5. My 7-11 used to sell 2/$2.50, which was amazingly cheap buzz. I like the full body of an 8% lager compared to how watery the 5% beers can be.