What is Best Buy "Calibration."?

I just got a Samsung LED TV, so I was at Best Buy today just checking things out to get ideas for it.

I saw to identicle LED’s hooked up next to each other, one looking better than the other (slightly), with a massive sign that said, “Let Best Buy come calibrate your TV for the best bang for your buck” or something along those lines.

What could they possibly do to make it worth the astronomical price I am sure they charge for it?

Obviously I’m assuming it’s another one of their overpriced scams (don’t get me wrong, they are a great place to shop sometimes and where I have purchased every TV I have owned as an adult). So assuming it’s a way to get money, what could they possibly actually do so they could say they did something warranting a trip out to your house?