Until the last season or two of AL, stores and event organizers were given free access to the adventures. And stores and events had the option to not charge at all to play. When the adventures went onto DMs Guild instead and everyone who no longer had access to the free versions, and who wanted to run the adventures, needed to start charging something to cover their costs. Baldman Games is still fairly new to the organizing and running of the games at conventions, so they are still probably feeling their way to an acceptable price to play, though I am sure the cost will vary based on the size of the convention, as the higher the number of players, the higher a price they can charge and still fill the tables.
Paizo, on the other hand, has always charged for the PFS adventures and they have had several years to figure out a reasonable cost to number of players ratio and can charge a more reasonable price, even at huge conventions. Plus they have made their money back many times over on the early PFS adventures, which many people still play, and can charge a lower price for the newer stuff because of that.
