gameon: The one that is hardest for me is Euros. Because of GOG i have a decent amount of what the dollar ratio is, but although i know the euro is less than a pound, i have no idea how it stacks up to the dollar.
But with online converters, they usually get the amount right. It just takes longer to work out whether games are worth buying or not at specific prices.
It's even harder here, because I have to convert it to czech crowns first. ;-) So I have to remember that dollar is around 20 czech crowns, euro around 25 and pound around 30.
But sometimes I want to know how much a game costs in dollars when it's in euros or pounds to compare it with price elsewhere, so I have to do even more converting. :-)