a $50 head unit? That depends on what the product is and the quality of said product.
If you want a head unit in your car, I (varies with other people) would only trust a reputable name brand, such as Kenwood, Alpine, and Pioneer. Actually, those are the only three I would consider buying. The head unit I have in my car is a Kenwood KDC-MP242. You do not have to buy from those three only. I have seen other good ones too.
I personally wouldn't buy anything from Wal-Mart that ran off my car's computer unless it was name branded accessory like an iPod or phone charger, and some male-male audio cables. Other than that, go to Best Buy or a car audio specialist to purchase a head unit.
Do some research before you go into the store, do not trust employees, because lots of my experiences dealt with people who glorified a product. Look for customer reviews, build quality, features, price, and compatibility. And if you're feeling up to it, decide if you want to install yourself or have a professional do it. Installing a new head unit in your car will require you connect a bunch of wires, (and depending on the car) taking your dash panels apart (note that you may only have to use keys to slide your unit out of the dash, depending on the car), and wiring.
My head unit was $150, and you can probably get it on the internet cheaper. I'm in love with it and have had no problems with it whatsoever. I would actually recommend it.