Quick: which is cheaper?

The Man should mandate that retail price comparisons (on the shelf, and in advertising) be standardized at dollars per liter versus price per unit. Will this happen in my lifetime? Not a chance.

I love reading grocery ads to try to determine who has the best prices that week. Yesterday, I needed Diet Coke and milk, so I opened the paper and had to guess which was cheapest:

1) ten 2 liter bottles for $10;
2) two 12 packs (12 ounces each) for $6;
3) two 6 packs of 0.5 liter bottles for $5;
4) one 12 pack (12 ounces each) for $2.99;
5) one 2 liter bottle for 79c

Sure, I could've tried to do this in the store, but the Unit Price is often hard to determine, since the store calculates items differently (the "unit" in a 12 pack of cans is the price per can, not the price per ounce, and then how many ounces are in a liter?)

So, I converted everything to dollars/liter to find:

qty	volume	price	$/L
10	2 liter bottle	$10	0.50
2	12 pack 12 ounce can	$6	0.71
2	6 pack 1/2 liter bottle	$5	0.83
1	12 pack 12 ounce can	$2.99	0.70
1	2 liter bottle	79c	0.40
1	3 liter bottle	1.79	0.59

Next, I compared two ads for milk:

qty	volume	$ price	$/L
10	64 ounce	$10	0.53
2	1 gallon	$5	0.66
1	1 gallon	$3.19	0.84

I usually buy the 3 liter bottle of Diet Coke for $1.79, and (if I can't find it on sale) the gallon of milk for $3.19 .. which explains the last entry in each table.