Alternators are generally not wicked expensive as far as car parts go, but a couple hundred is still a couple hundred.

Did you look under the hood? One time I thought my car died (on the Brooklyn Expressway no less), but it turned out the positive connector was just loose (one of the officers who was directing traffic around my car noticed it). If you can see the battery that sort of thing should be visible even if you don't know jack about cars and easily fixed as well (just tighten a bolt and you're set).