Maybe they can charge to park and not for powerAgree with MP3Mike, pay-as-you-go means a whole different payment system, compared to a lump sum you can activate in-store or even through mytesla. In some areas, to be able to charge someone for electricity requires you to be considered a utility company, not a car manufacturer, which overall brings more cost than the revenue from a pay-per-use system.
I think it'll be around 1000$ for long distance supercharger usage for the smallest battery, and probably included in the first battery upgrade.
Sometimes I saw cars parked without charging because they already finished and the owner is still at the stores