Too many people tend to compare everything to exclusives where they tend to get 2x value right after it's EOL. Well, this is the only true exclusive in the LOTR/Hobbit line. But not everything is a HH, or SSD.
Ive beaten this horse a few times now, but I really think the ToO, The LM, HD, & UG are going to be the "premiere sets" where you will get about 3x above retail a couple years from now. I also think Shelobs attacks, Council of Elrond, Wizard Battle, Black Gate, Mines of Moria, and Lake Town Chase have potential to go in the 2x to 3x range. Shelob is already in the 2x range. The pirate ship ambush is a weird one... i'm not sure how that one will go, but lately it seems to be popping at retail rates on ebay, and I just scarfed a few of those below retail last month when I stumbled onto them at clearance in a walmart. So, that set has yet to truly go dry yet (you can still get them in various TRU's), but it might also have potential, and it's one of the last LOTR sets you can still find at retail, other than the ToO, and perhaps the Black Gate.
But have no fear with the tower. I really do think it's going to do very well. Now, if they will only take that one "Ideas" concept of the Minas Tirith that's currently under review and make it into an exclusive, before they retire this line, i'd be absolutely jazzed about what this series produced. I personally, don't hate on the Mines of Moria, and some of the other sets. I think they did a good job, considering they presented a range of price points for sets, and a variety of sets. Not everything was a castle, but there are a few good castle type sets in this series. I think it's a good line.