Posted November 05, 2012
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Suppose a tier costs 40 dollars. Amazon charges you 40 dollars. To complete the transaction, the bank sells you 40 dollars, taking your 32 euros plus a cut and giving Amazon their 40 dollars.
Now suppose a tier costs 25 pounds (~40 dollars). Amazon charges you 25 pounds. To complete the transaction, the bank sells you 25 pounds, taking your 32 euros plus a cut.
You never ever win money when you pay in another currency given a static exchange rate. Euros and dollars are just different units of value. For example, in today's exchange rates, 40 dollars = 32 euros = 25 pounds. If something is (in your opinion) overpriced in pounds, it will be overpriced in dollars or euros.
Now, if, say, the euro rises compared to the dollar and prices lag behind, it may be that, for a time, buying (for example) a computer in the US will be cheaper than buying the same computer in France. But kickstarter projects are unique; this does not apply; you just look at the price, work out how many euros you'll be (probably) charged and decide whether it's worth the money or not. When you pledge for a tier, you carry the risk of the exchange rate changing for the worse, but it's true for dollars as well as pounds.
Also, it may be that the bank takes a higher cut when selling you pounds. But, unless some stupid fixed fees apply, the difference is no higher than 1.5-2%, which is seriously negligible against your intention to pledge for a kickstarter in the first place. Especially if you get to save on shipping.
You're purposely using the same converted amount (EUR) in your examples, with different tiers.
Here's some other examples with today's rates :
$20 tier => €15,64 + €1 + €0,42 = €17,06 withdrawn from my account
£20 tier => €24,97 + €1 + €0,67 = €26,64 withdrawn from my account
Almost €10 more, that's not negligible. My main concern is about accounting.