Aren't they marked up if they know you're a foreigner.
There is little benefit to me in bargaining my way down to $25 - yeah they might think they've conned me, but (as long as it's not factory made junk) I'm happy to pay $50 for something that I like, even if I could negotiate it down to $25. The $25 saved simply doesn't mean that much to me in the grand scheme of things, but most likely does to them.
In the case of online goods they have a price X in USD because that is the currency the seller has / uses. They sell it to everyone at that price, they don't upcharge people who have to convert currencies.
Now, it is very well possible that those people will have to pay quite a lot for it, but that's because they buy from a seller based in a region that's financially better off and as such has higher prices in general, not because the seller tries to get as much as possible out of them.