Despite them being a EU member state, they don’t use Euro as their official currency. Since they have their own currency being the Zloty which is considered stable, but even if you have Euros or US Dollars for converting to Zloty: does purchasing power hold up since both Euro & US Dollar possesses a higher rate? I figure that Warsaw will be expensive due to it being the capital, so that is expected.
You have to be careful with the Big Mac index. That’s a foreign delicacy in a lot of places, and there might be a guy selling a nice meal for a fraction of the price on a street nearby.
In Europe it might work.