Non-web person here: No idea that Google Maps costs money for anyone, assumed it was ad-supported like anything else.
Had we had more time I probably would have looked at doing our own implementation using leaflet and Open Street Map. But that is a pretty big project to throw in when are in the middle of a year long roadmap. I assume this played into Googles strategy. Give them enough of a heads up, but not enough time for most to move away.
I think the service used to only really impact medium-to-big sites, but the price change basically impacts any site. After 25,000 map loads (page hits) you start incurring some substantial fees.