Think about it.. It's one industry Wal-Mart is seriously lacking in and can come in with their economies of scale and absolutely crush competition by squeezing margins like they do in their retail stores, offering an "introductory pricing" to steal market share then when competition is weak, raise prices. It's the Wal-Mart strategy and it works every time.
Companies are willing to take a hit on their products for a short time if they can get their products in the largest retail chain in the world, it makes sense.
Edit:
The biggest damage done to those companies is the price matching strategies offered to maintain market share. They end up taking a hit cuz their overhead is greater than Wal-Mart's.
The types of people who typically buy (more) expensive electronics at Wal-Mart already know exactly what they're looking for or going to purchase. The specialized stores tend to have the window shoppers and the ones who don't turn into a sale typically don't because of the high prices associated with the knowledgeable staff, customer service, other services offered and specialization.