Цитата: Mark240590they cater mainly for the American market.
Absolutely.
As a general rule every old coin is worth more in its own country, as the collectors are more numerous and the demand is higher.
My best bargains are medieval Austrian and Hungarian coins from Poland; I bought some France medievals and Swiss cantons coins in my home country (Hungary) and two weeks later I sold them in Geneve for 3 times more. ... and cheapest (original!!) Habsburg Thalers I bought in Cairo.
Never buy Ottoman coins in Turkey, but that is a great place to sell them!
So, use NGC with moderation outside the US!