Prices for EU players not using Euro

[Vellrad]

I want to use that nice promo, but here goes my question:
Which price do I use? 50USD, 40EUR or 34GBP?

I'm asking because there is a difference in values of theese money- 6,9k points costs 155,57PLN when paid in Euro, 150,92 when paid in pounds, and 138,47 when paid in USD. To this, there is also some bank provision added, for currency exchange (damned scammers :/).

I hope I'm paying equivalence of $50, but I don't know for sure.

[Rumbaar]

Pay using the currency that offers the best exchange rate for your location. For example the Australian Dollar is strongest against the US Dollar at the moment. So I purchase all mine in US Dollars.

[Vellrad]

Pay using the currency that offers the best exchange rate for your location. For example the Australian Dollar is strongest against the US Dollar at the moment. So I purchase all mine in US Dollars.

There is no choice.
I'm paying using my local money, I wonder to which currency it is turned by banks before beign given to turbine.

[Rumbaar]

It shouldn't be turned into anything, what is displayed is what your bank turns it into.

For me AUS Dollars is never displayed, only US. So my bank turns it into US dollars and I get a currency conversion fee from my bank.

[Vellrad]

OK, I've checked it.
Instead of 50UDS i must pay 39 euro, which is 25% more (because bank is taking aobut 5-10% for currency exchange).
Why prices are listed in currency than nor I, and nor Turbine uses?