That logic does not hold up - as other sites are offering it (including city states) for less than listed here on Amazon. Seems that Steam just has a very high price for some reason (maybe because the publisher sets the price rather than the retailer I think, on Steam).
That being said it would be nice if Amazon would confirm one way or the other on this.
*Edit - actually I note the pictures include a Greek States DLC one - so looks very likely this does indeed come included. It was stated by CA that *all* preorders would get it (ie it is a bonus for preordering, doesn't matter where from) so it wouldn't make sense if it wasn't on here too. Ordered!
I just watched the trailer on youtube and in the description is said "What's more, those who pre-order from any participating retailer will get access to the Greek States Culture Pack for free -- one content pack, not split across different retailers. Simply pre-order and they're yours."
Steam will likely do one of their three stage pre order specials when it gets a bit closer but i really dont understand how they can set the price so stupidly high as everyone else will just be sending a CD with a steam key