Let's see. About $175 for the "best" Wal-Mart bike. Then, about $75 to have a good bike shop take it apart, grease the headset and the wheel bearings, assemble it correctly, true the wheels, adjust the shifting, and adjust the brakes. Now, for $250, you have a bike worth about $100.
There are lots and lots of good used bikes available for around $200, some of them comparable to a new bike selling for $600 to $1,000. And, a lot of times, an LBS will have a hybrid for around $250 from a major company, with a good warranty.
I'm often amazed when I'm in a bike shop, and someone is looking at a $250 bike, and says "That is a lot of money for a bike", when that same person drove up to the shop in a Lexus, a BMW, or a Suburban. I'm tempted to say "And, $40,000 is a lot for a car...a used Yugo goes for $500".