So which is it, you "can replicate" or "tested this all over the US and no one has this issue"? Sounds kinda contradictory.
And no it's not "googles side". As I mentioned - and you would have noticed as well if you really "can replicate" - other games manage to show the correct price for their in-app purchases on the same exact device or emulator that is showing incorrect price for Gravity. So it's not Google's fault that your crack team of developers can't figure it out.
For example, Bubble Witch 3 Saga - give it a try and let us know if you still think it's Google's issue.
And no, I'm not using a VPN although I can believe that a VPN could help replicate the issue if it's really caused by currency conversion. And even assuming it is - that still wouldn't make it right for the game to show one price and then charge a different price. Not sure why you're still arguing such a simple concept and trying to put the blame on Google.