Microsoft try to limit the geographic distribution of MP2002 and 2004 - so there's a good chance its the same with 2006. Eg. Amazon UK would refuse to ship to North America.
I see that Grey Matter (based in the UK) have it for about GBP200:
greymatter.com :: MapPoint 2006
(most of the editions, eg. Fleet Edition are order-only, but the retail version is there available for sale if you scroll down).
GreyMatter shipped MP2002 Europe to me a few years ago.
Richard