When I was traveling in Mexico, it drove me nuts that even though I was signed in, Google Flights switched my currency from dollars to pesos every single time I opened a new tab! I think they really don't care.
Oh, "local" as defined by your IP too, so enjoy your VPNs.
The only solution is using the website instead, it has a currency dropdown.
Edit: after typing this realized this isn't ip, its provider. That maybe does make sense to cue off of.