The Rise of Isengard will be available for Turbine Points sometime, so as a lifetimer, I can just wait and get it for free. They are encouraging you not to do that with pre-order incentives including a pocket item that gives +25% xp on monster kills. They are also heaping on variations on a small set of cosmetics. If you are not a subscriber, the “Legendary Edition” is a pretty nice deal, coming with quest packs for the Trollshaws, Eregion, Moria, Lothlorien, and Mirkwood. That is just short of getting all three expansions for $50, plus $10 worth of Turbine points and all the cosmetic candy. Player-compiled Q&A here.
A +25% item seems pretty big to me. It works up to level 65, so for every character you make until they reach expansion pack levels.