Prices in the Microsoft cafeteria are often illogical.
For example, a "special sandwich" costs $4.25. A piece of whole fruit costs $0.50. But a "special sandwich with a piece of whole fruit" costs $4.95.
If you're not careful, the cashier will ring it up as a "special sandwich with a piece of whole fruit" instead of as a "special sandwich" and a "piece of whole fruit".
(I think they eventually fixed this after enough people complained.)
As another example, name-brand bottled water is available in the cafeteria. You can get a 20-ounce bottle for $0.99 or a one-liter bottle for $1.99.
One liter is a little under 34 ounces. You're actually better off buying two 20-ounce bottles than one one-liter bottle. Get more water and save a penny.
(For those who have a Wall Street Journal subscription, you can read more about how corporate cafeterias maximize profits in the article Nowadays, Companies Make Money Off You, Right Down to the Last Bite from the 13 November 2002 issue.)