For the longest time, Alliances had a very unbalanced distribution of cards with financial value. The most value was usually seen in Force of Will, with the card fluctuating around $70-$110 for most of its time on the market. There were a few other cards that held value similar or nearing that value, but up until the last five years the movement on those lesser cards were minuscule. I remember hearing someone say that opening a box of Alliances was basically Force of Will or bust.
That statement being a vast oversimplification of the facts, with several cards holding ten bucks or more for a vast majority of the lifespan of the product, but it does hold a small aspect of truth. The value of Alliances as a set has evolved a lot in the last five or so years, and even more so with the massive rush on Reserved List cards in the past 6 months. This exponential growth in value, coming from a place of low value in most of the cards in the set, has allowed it to be a very interesting entry point for some investors.
The expected value of the singles of one sealed box of a set is based on probability, and how much people want the cards that are available. Simple supply and demand right? Not really. With the pull rates in two given boxes varying slightly, you can't ever fully predict the value of a single booster box. Alliances further complicates things with multiple rarity classifications. Force of Will appears twice on the uncommon sheet, with a 110 card uncommon sheet. This leaves the odds of a Force of Will being in any specific uncommon slot in a single pack being around 1/55. The packs themselves held 12 cards with 3 uncommon cards among them. One booster box of Alliances contains 45 packs.
This leaves a 3/55 chance of pulling a Force of Will in a specific booster pack of Alliances, which means that in a whole box it is likely for you to pull around 2-3 Force of Will's in any given booster box. This meant that the margin's for making back your money, with the minimal to non-existent value in other cards in the set, and the astonishingly low price of an original Alliances Force of Will, are very low, making this set primarily a sealed investment for most, as box supply diminished, sealed prices rose, and a false sense of abundance for singles was established.
What stays down...
This set was released almost 30 years ago. There 31 reserved list cards in Alliances. A set with 150-ish cards in it, having 31 cards on the reserved list isn't necessarily crazy on its own, but in combination with other factors, including the undervaluing of the majority of these cards, has made buying a decent amount of reserved list cards for dirt cheap is very possible. Even now, the 3 lowest value reserved list cards in this set are all under $4.
However, with the reserved list itself seeing a steady increase over the past year, with massive spikes in the past couple of months, it had to happen sometime. With RL cards this cheap, it's a no-brainer that they would eventually rise. The market incorrectly priced most of these cards. A set this old, only one card over 60 bucks? This isn't Fallen Empires! Even with the non-reserved list cards, you have some value with Elvish Spirit Guide. Something had to change, and with a set that old, with the existing level of value, it didn't make sense for it to go down any further. People saw the discrepancy, and it was soon corrected.
As an entry point into MTG Finance
As a lot of newcomers are entering the MTG Finance space, new investors are always on the lookout for the next quick buck. The quick gains make sense to most new investors, and can often teach important lessons about investing long term, the risks of participating in the market, and the risks of not doing so. The easily quantifiable gains allow new investors to see the value of these investments if not portraying them a tad unrealistically.
With a large number of cards experiencing gains, and those gains being consistently high across the board, it's an easy starting point for those new investors to acquire a decent amount of inventory without much need for searching around, or much cost. With the potential to grow possible, it also stands well as a long-term investment. This low-cost ceiling and high invest-ability make Alliances a great set for newcomers to focus on, and seasoned investors to take advantage of as well.
What about other sets?
The main advantage of Alliances over other sets is primarily the massive mispricing of the set as a whole. This set has been undervalued for far too long. With Mirage, for example, there are significantly more Reserved List cards, and heavy hitters like Lion's Eye Diamond bring the rest of the set up with it. Alliances stood as the set that people viewed as Force of Will or bust. People underestimated the set based on what they remembered it as always being. That is the main advantage. Everybody likes an underdog, but few like to root for one in the moment.
There is still lots of room to grow with Alliances in my personal opinion. The fact that cards like Lake of the Dead and Force of Will are as cheap as they are is astounding to me. With the other cards in the set of particular value, a lot of them hold value for mostly speculative reasons, but lots see at least fringe play, if not more mainstream use. The best time to get in on something is always yesterday, but today is always second best. With Bitcoin people always say that the best time to hop on is right now, and that very well holds true for Magic, for now at least. The statement that amateur investors can get a good start with Alliances seems to hold true as well. Remember to be smart, be fiscally responsible, be thrifty, and invest in cardboard. Have a great day.