They did pretty nice analysis and found out their whole infrastructure costs $1300 a month and they would have to pay additional $5000 for Google Maps alone (right now GM costs them nothing).
Looks like GM will be ~10x more expensive to them than Mapbox or MapTiler, here's the original article (in Polish) translated by Google (sic!):
https://translate.google.com/translate?sl=pl&tl=en&js=y&prev...
Looks like many folks who leeched on GM's free plan will move to alternatives so maybe this dick move will turn around and became actually a good thing, would love to see more competition in the area and right now Google Maps is years ahead of competition: https://www.justinobeirne.com/google-maps-moat