Promoting locations, whether commercial or not-for-profit in scope, is not quite what is being done here. Yes there is a commercial aspect in Waymarking that is forbidden in other GPS games by Groundspeak
but the purpose of exploring any Category is that you have an interest in the content.
Often I go for the Waymark, and leave with much more than an icon. To say that it cost me $75 to enter Walt Disney World to claim the Visit or $4.99 for a Big Mac combo is really not the best way to think of it.
Spending $10 per person to go to a local Racetrack (there is one Waymarked here) for the family then documenting our experience is my focus, not that the track got $30 out of my pocket due to some free advertising that they didn't even ask for. Sometimes I am surprised that some commercial ventures haven't latched onto Waymarking and populated some of the existing Categories since they would have most of the data already. Like you say, free advertising and it might actually bring in customers. And me, I'm all for that too cause it will give me more places to go!
BQ