How to ebay fees work?

[tobiaboum0]

To sell some camera equipment, I decided to use ebay. I strongly based this idea on the ebay fee calculator. It turns out that this calculator is grossly inaccurate, and I'd like to ask whether this is "normal".

Anyway, I sold for some 3850 euro, and I had to pay a whopping 520 euros commission over this amount. On my invoice it states "actual selling price 1800 usd, which corresponds to a commission of 180 usd = 153,23 eur". That's something I can get around. Now, the actual value on my invoice reads "185,41 eur". This means that my conversion rate from usd to euro is a whopping 1 to 1 - something I would never agree to had I known previously.

So my question is, "is this normal?" and obviously how can I get this number before I decide to sell, so I goddamn know what I'm getting into.