A library card is typically a flat fee, and you can perform as many 'searches' as you want. In a bookstore, you can ask the clerks if they have books on a particular topic, and they will show you their wares. You can browse covers and abstracts for free, to help you decide whether anything is worth purchasing. Wouldn't that be a better model for PACER to follow?

Or think of it this way... how often would you go to a library or bookstore that charged you simply for looking around (additional charges apply for each aisle you walk down)?