Many of you, like me, are always on the lookout for the next big thing that could make you millions of gold. I believe that that opportunity has presented itself with a very low risk option. Vials are currently only used for crafting Nekro in the game. It is also only able to be farmed in the arena (very easy to farm at the moment) and tombs in which the drops are quite a bit less frequent. There are several ways in which the price could shoot up.
1: STS decides to scale arena bosses which would eliminate the PUGs that are currently able to run it, which would cause the production of vials to nosedive.
2: STS nerfs the drop rate of vials (not as likely, but is possible).
3: STS uses vials as a component for some new powerful crafting item akin to how they brought back arcane fragments. I believe this is the most likely scenario since everyday players farm for vials and STS would really enhance the economy by giving the middle of the road player something more worthwhile to farm for.

Now I will discuss the risk vs reward. Vials currently sell on cs for 11-12k and have a vendor value of 10k (which is set in stone). This means that even if none of these three events happen, you can vendor it off and still have 80-90% of your original investment. However if any single one of these events happened, the price would likely triple or quadruple to 35-45k. A very likely scenario in my opinion is events 1 and 3 both occurring. Both of these happening at the same time would drive the price up to likely over 100k/vial.

In conclusion vials are a great investment both because of its limited downward mobility (maximum loss of 10-20%) and high upside potential (returns of 1000% or more are possible if certain scenarios play out).