Single post in PSA Regarding Paypal and DeviantArt

I'm confused by this. So say I was purchasing something for $20USD and since I'm australian, I have to pay currency conversion as well since USD>AUD. So $20AUD is not equal to $20USD, but paypal charges me a fee as well as conversion for the seller to end up with what they asked for in USD. Does that make sense? Or am I just reading what you meant wrong? Because I just assumed it meant they just had to pay the seller's fee initially.