It could be because of the competition over at Amazon. Each seller trying to outbid the other by dropping the price in small increments. At current prices they are just under $30 dollars. Certainly the quality of the Baofeng UV-5R radios and accessories is worth the price tag. You get a dual band handheld radio with high capacity batteries, speaker mics and other accessories and still spend less than $50 dollars.
One of the reasons the Baofeng UV-5R radios may be so inexpensive is they are not aimed at a specific Niche, therefore they save money on big advertisements and promotions like the ham radio equipment manufacturers like Yaesu Icom and kenwood. They also do not test and advance any technology. They built the radio on existing technology in a way that works okay for most. They also have no research and development costs.
Of course, the final decision is up to ham radio operators whether or not to purchase a baofeng UV-5R radio and use it on the airwaves. Since Baofeng is not aimed specifically at the ham radio market, they would probably survive if no amateur radio operators purchased any of the equipment offered from baofeng Radio. The UV-5R does make an interesting toy to play with, and with a price tag that low most ham radio operators just can't seem to help themselves. Curiosity kicks in and before you know it you have a Baofeng Radio sitting on your desk.
When you purchase a Baofeng UV-5R radio you get a decent dual band handheld radio, an 1800 MaH battery pack, the cradle charge, a dual band 2M/440 antenna, belt clip and the wall wart. It also comes with the programming software on CD ( you can toss that and just use CHiRP) a lanyard and a 120/220 plug adapter (remember that the US is NOT the main market).