In all fairness Best Buy is getting better with their pricing in a lot of areas. TV's, Blue Ray players, etc are competitively priced. Here are some tips on how you can shop at Best Buy and make out like a bandit.
First don't EVER buy a cable from there. Certainly do not let some sales man talking you into buying a "Monster" cable for your HD TV. You'll hear things like "You just spent $1500 on a TV you want to have the best picture possible and lower priced cables may give you a poor picture." - BULLSHIT it's HD and all digital. Which means your cable is either going to be rated to work or it wont. Monster cables are no better than the cheap ones. Case in point, the cheapest 6' HDMI cable I could find at Best Buy was around $25. "Five Below" a $5 and lower store across the street sells a 6' HDMI cable for $5. Guess what, works like a dream on my Xbox. It's also fully rated for 3D TV. You can also get them at a reasonable price at Amazon.com. However my favorite place for cables is monoprice.com. They sell cables of all types dirt cheap. Cat 5, HDMI cables you name it. If you can wait a few days for shipping you can save a lot on all sorts of things from there. Don't let some salesman convince you otherwise. The same applies to optical and coaxial DVD connectors. Digital transfers 1's and 0's.
Best Buy does price matching just like Wal-Mart and most other retail chains. What most people don't know is that Best Buy will match Amazon's pricing. It's the only brick and mortar store I know that actually will match Amazon.com's prices. I've saved, $20, $30 and even more on products by pointing out that Amazon sells it for cheaper. Now if you have an Amazon Prime membership you can get shipping for free and get it in two days plus you dont have to pay sales tax. That is the best savings but some things like a TV you might not want to received from UPS's fine delivery staff. You can however go right to Best Buy and point out it's $200 cheaper on Amazon. The only catch is you're on the hook for sales tax but hey, you can get it same day.
Another good use for Best Buy is on fixed pricing items. These are items like a new Wii, Xbox or Playstation. They will cost the exact same amount regardless of where you go. That way retailers all make the same amount on the item despite which retailer you go to. Best Buy though has a rewards program that Wal-Mart doesn't so if you do end up buying a lot of equipment you can end up getting a few perks in the way of some free cash to spend at Best Buy. Something for free is always better than nothing.
Competition is tough these days with electronics retailers. Information like this should give you an edge when buying new equipment.