Welcome to Lego Investing. I have been in this game since the 1990's and my prime years were from about 2004-2007. All I can tell you from all my years of collecting and ebaying is that there is no guarantee, but the large lego sets are the closest thing to a guarantee as you can get. While not every Large set is a home run, you are pretty much guaranteed to NOT lose money, which is more than you could say than any other investment. Legovesting has become increasingly popular in the last 3 years, making it more difficult to make money as fast, and Ebay fees and the post office are continuing to cut into profits heavily, but you can still make good money. Just not as much and as fast as the mid 2000's.
There are many naysayers on this forum about the Tumbler and they have their reasons. I personally believe this is as sure a bet as any due to the fact that despite what many people on this forum state, the interest for this set is VERY HIGH. It has more reviews than almost any other UCS set that was out for only 16 months, and has been a consistent top seller on Amazon since it has been out. While more interest drives more people to hoard, there is only so much supply out there, and this was hoarded less than many of the other sets out there. While the extra couple hundred resellers that picked up the set to resell will cause this set to take longer to sell out at lower price points, once it does, it will rise higher than the average 200 dollar set.
Right now there are only 78 resellers for this item on Amazon. That is much less than Red Five, DS or many other UCS level sets. The set is already up to 300+shipping on Amazon which again is higher than Red Five or any other set retired in the last several months, and it's only been sold out a week, and there is even a small trickle of supply likely secondary to returns. The set was only available for about 16 months before retirement which is about 8-12 months less than the average UCS Set, again decreasing supply.
People state Batman is not a "popular" commodity or as popular as Star Wars or Jurassic Park. While it is not at the level of Star Wars, it is very high. Batman has been popular in a tv format since the 60's and more popular in comics for lord knows how long. Batman has had 7 and soon to be 8 movies made, and will continue to have movies made. Batman will always be at the forefront of people's minds. People state that the Nolan Batman trilogy's time has come and gone, and thus interest in the Tumbler will die. Well look at the Delorean!!! Hasn't had any reason to be on the forefront of people's minds in 20 years except it was the 30th anniversary recently and people are paying 150 for some dinky little car that doesn't even look like the real thing. People state that no one will want to buy a Lego model of a car featured in only 2 Movies. Again, I point to the Delorean. The Millenium Falcon is only in 4 movies! The Super Star Destroyer in just one. The Nolan Trilogy is one of the definitive trilogies of the 2000's and is revered. It was a box office monster. The Heath Ledger Joker is one of the most legendary performances of all time. Batman, and especially The Dark Knight is HIGHLY RELEVANT and POPULAR. Especially among the crowd that can afford a 300 dollar lego set.
This set will do well. How well is the only question.
Lego investing is one of the safest investments out there because the number of Lego fans, unlike almost any other toy out there, will always continue to grow. Lego is not a Fad. It is not a beanie baby or a furby. It is a time honored toy, in which a lego from 1950 will still interact with a lego from 2016 the same. Lego never dates. While building techniques improve, (just look at the early X wings and first Star Wars sets, which I bought all of them when they were first release in 1998) a Lego from 50 years ago still functions the same as a lego today. With a constantly growing fan base, there is a constant stream of people who are becoming new to lego. With a constant influx of new Lego fans, there is a constant stream of AFOL's. Lego has always been a "higher" end toy as the prices for legos are higher than an average toy of the same size. Because of this it is a toy that tends to skew more toward the "upper" and "upper middle" class. Because of this, there are always children who grew up with Lego's that have a high likelihood of making a good salary. This leads to more AFOL's who when they start earning those salaries want to capture the magic of their youth, and also share it with their children. They then buy the sets they couldn't afford as a child, and then further the resale market. For many of these people, they will pay whatever it takes to get what they want.
Lego is one of the most unique toys out there and it's ability to withstand depressions and stock market crashes makes it one of the safest investments out there.