For a charger, all you care is a clean 5V and an output from 500 mA to 1 A (1000 mA).
Some of the guys around here have metered their chargers and have found them swinging voltage around.
So - it's not the price, it's the quality - just like always.
Monoprice.com has a great rep for selling _good_ stuff for inexpensive - you want inexpensive, not cheap.