I'm from Europe myself, and it usually costs us anywhere from $40 to $150 to travel anywhere in Europe, though the prices do go up if you want to go to a place such as China, Thailand, or even India. But then again, that's Asia!
Prices are much lower for closer distances - it's not at all unusual to be able pick up ~$150 round trips for shorter routes.
I could pay less, but I stick with US Airways so I can rack up miles. When I made less money I'd fly whatever airline was cheapest - just under $400 was common.
I've done it all: bus, train, and drove myself. Flying is the best deal, hands down. There's no comparison - round-trip cross-country for $500 is a modern miracle.
I live near Washington, DC. If I fly to, say, New York, then $500 would be outrageous. I'd expect to pay $100-200 roundtrip for that, depending. It's about an hour's flight.
If I fly to Miami, I'd expect to pay $200-300. That's about two hours.
If I fly to San Francisco, then $500 becomes a reasonable price. That's a six hour flight.
It makes no sense to talk about "a plane ticket" in isolation. From where to where? How far?