Can confirm the other comment. TV's are very low margin. It's not uncommon for them to sell at a loss, or even severe loss (if you're buying other higher margin items).

Audio isn't typically so bad, but I think it depends on the systems.

The "home theatre in a box" items outside of Bose tend to be pretty low margin in a lot of cases.

Real amp/stereo/surround setups can be pretty decent margin.

My knowledge is derived from a smaller, mid/high-end outfit, so I'm not too sure about Best Buy but I assume the TV's are about the same.