Don't forget VAT
Nobody said its going to be trivial to calculate, reality doesn't care about that.
Yes the exact cost will differ depending on what you buy but that doesn't remove the cost, it just obscures it - which is the point of having so many different taxes.
I've managed staff all over the US and in Europe and have had access to large corporate pay scales across zones. The difference is so significant that CoL is a total rounding error for software developers.