[robjan]

A Forex trade is still taking place so there must be a counterparty. The USD don't just disappear and reappear as EUR. Someone is buying them on the other side. Getting a better rate implies the counterparty getting a worse rate.

[_iswk]

I'm not sure I understand your criticism. The USD is used to buy BTC. The BTC is then sold for EUR. There's no Forex trade, not directly at least.

[robjan]

If x EUR is worth y USD, any discount results in someone losing money or taking on Forex risk through some derivative product. It doesn't matter which settlement layer is used.