You could, but you won't. We're not able to buy all ads, so for most people $2 will last a good while. For reference, the average US web user sees ~$5.60 worth

You could, but you won't. We're not able to buy all ads, so for most people $2 will last a good while. For reference, the average US web user sees ~$5.60 worth of ads per month. Of those only 40%-ish go out for auction, and of those we buy as many as we can.