You should pay more if you use more. But that charge should be appropriate. Gigs cost fractions of pennies, not multiples of $10. You have a 50 dollar, 250 gig package from your provider, you're paying $48 bucks for the infrastructure, upkeep, profit, fees and a dollar or two for actual usage. You go over that 250 gigs your bill shouldn't spike. Even if you use another 250, your bill shouldn't rise more than a few bucks. Not the multiples of the $50 you paid for the first 250. It's price gouging.

It's like getting a 10,000 gal of water for $50 a month and then $10 a gallon if you go over.