As it currently stands, the online store contains a bit of a trap for the unwary: if you buy the Helm's Deep expansion (and only then) you have the option of buying the expansion quad-pack for a 50% discounted price.
Unfortunately, I wasn't aware of that until I clicked "purchase" on the Helm's Deep expansion, so I ended up paying full price for the other expansions. This information may very well be available somewhere, but I think it should be so visible as to be impossible to miss. For example, any attempt to buy the quad-pack (or any of the previous expansions) on an account that doesn't have Helm's Deep should trigger a pop-up warning before proceeding to purchase.
Anyway, I hope this stops other returning players from making the same mistake. Now feel free to mock me
(PS for Turbine: I will accept a £15 refund in ale or pork scratchings down my local on Fridays between 6-9pm. It's only fair.)