I got a good deal on some "generic" tubes from Nashbar or Performance. About a buck each. Two or three times a week, I'd have a flat. Often a rupture along a seam. Or, a rupture where the valve was attached. Or the valve just came off. Or, the valve failed up at the seal.

I switched to "expensive" Continental tubes. Not a single flat in 2005, for any reason...not even nails, glass, roofing tacks...nada (knock on wood). My math indicates that a $5 tube that lasts a year or so is cheaper than a buck tube that last two days.