According to this article (http://www.theregister.co.uk/2011/10/27/google_maps_api_no_longer_free/) keeping Google Maps would cost $4 for every 1,000 visitors. If one in every 1,000 cachers is a PM, why not simply increase the PM cost from $30 to $35? Or increase the cost for PM to $35 and only let the PM use Google Maps.
I'm relatively new to Geocaching, and I have been spreading the word like crazy to my friends, family, and coworkers about how great the activity, community, and Groundspeak in general is, but this change has really frustrated me. With as slow and buggy as the maps are right now, I can't imagine those I talk to working through the pain of these maps to get started caching.
And just as a side-note, if Groundspeak had initially sent an email out to Premium Members explaining the situation and asking for a vote for poorer maps or increased cost, I am sure the majority would have been in favor of increased costs.