I see bikes from the 1986 to 1990 era that have pro quality frames and forks, pro quality wheels, and Dura-Ace and Ultegra components selling for between $25 to $250. These bikes provide a ride quality similar to a new bike costing $900 to $1,500. In contrast, a $250 Wal-Mart bike is always going to weigh more, have generic brake calipers and hubs, and have numerous "non-standard" parts that will be difficult or impossible to replace.
I read an industry estimate that the typical Wal-Mart bike is actually "on the road" less than six months and less than ONE HUNDRED MILES during its total lifespan. The makers, understanding that, design the hub bearings, pedals and headsets for last for about one hundred miles of hard riding. A "pro quality" bike from 1986 will provide 25,000 to 40,000 miles of hard riding... by the mile, a 25 year old "pro quality" bike is a zillion times cheaper than a new bike from Wal-Mart.