The expansions are always sold separate from everything else however, if you go VIP then you get access to all content except for the expansion packs so that might be worth a look. Also note that in the expansion packs you get a bunch of points to spend in the DDO Store (2,000 from each expansion I think) which you could use to buy more packs. Also waiting for sales to be on will stretch those points even further.
Stoner81.