I think they do. It could fall under false advertising.
Corporate site says:
"Store Price Guarantee: Best Buy will match any lower advertised price from local competitors for the same product."
It doesn't say anything about, "Well, when we feel like price matching. It just says they do."
If they were smart, they would take a play from Walmart's book. Price match it regardless if you are going to lose money on it. A happy customer will always be back and spend in your store. Walmart estimates that the average joe will spend over 100,000 dollars or more in their lifetime at a Walmart store. To them, losing a few bucks to keep your business is no big deal because they know they will get it back. Seems to work for Walmart just fine.