Yeah can’t comment for local employees of local companies. Just have knowledge of UK & US companies hiring/outsourcing to Poland. It was cheap, not so much anymore.
If PLN depreciates against USD (as it has this year) and the contract is USD denominated (which is simpler for Google so likely the case) then you'll have actually received a gradual payrise!
Of course this is all hearsay. I don't know how real that figure is, but it's not particularly inspiring so I don't see why would anyone lie about it.