Similarly, I subscribe to magazines to get an option just in case I want to read any of the articles. The editors, for their part, arrange to have them all written just in case I do. Similarly, when dictionaries are all online, Random House could hold up the world's Scrabble players and copy editors. Unless, that is, there is competition that offers an exotic billing option known as the subscription or flat-price deal. It won't take a genius competitor to come up with this plan.
Advertising is, in effect, a funny kind of micropayment system.
Advertisers pay on the basis of how many people see their ad. For most media, this is measured statistically, via surveys, because statistical estimates are an even cheaper way to record tiny transactions. They're not exact, but the overestimates and underestimates average out over time. Ad rates amount to a few cents per customer impression, which is in the same range as micropayments. And of course the customer ends up paying, indirectly.