Car prices in USA...

[prongated]

...for example, I come across a 2001 Merc E55 AMG on eBay from a dealer which sells for under U$30,000. In Australia a similar car would cost twice that! And a brand new M6 for U$100,000? In Australia it retails for more than twice that plus on-roads! (M6 retails for about AU$270,000 in Australia including tax)

I'm not saying these prices are cheap, but I'm just curious...what gives? Such difference! It's not the luxury car tax in Australia, which is AU$32,500 on top of a AU$200,000 car...or am I missing something from these eBay prices?