Come on, guys. In all fairness, all expantions can be seen as mods. MoW Vietnam expantion is coming out, so is the MoW Vietnam mod.
As to the price, well I have no idea how much we are going to pay for AS. It is always better to wait a month or so coz the price upon the release is aimed at the rich and spoilt and then it goes down.
Since I love MP, AS offers more value for money for me than RT or Vietnam.