We Need More Writers!
A lot of people on our private forums have been arguing about what to do with Super Adventure Box Skins. Super Greatsword Skin is the most expensive one, and my advice for this one as well as all the others is as follows. (If you're not a member of the forum and my complimentary gold guide that goes with being a member... join today!)
Buy them during the last week of the event.
Sell them three months after the event.
I know you want to buy now and hoard for later, but so does every other person who's thinking ahead. The people who want these skins immediately are going to save up for it now and grab it by playing the super adventure. So your buyers are a handful of "super" lazy people right now. In other words, supply is up and demand is way too low. This is going to drive down prices, but that will all change when the event ends (but not before!).
I plan on buying one or two of each skin, then sell them off when they become super rare. If you look at Halloween skins, they are selling for crazy amounts of gold. Partly because they're awesome, but also because they have almost all been bought out. I'm not just looking at the sell orders either, but the buy orders as well for those skins. I remember when they were super cheap. In fact, I wrote a post once about flipping the shoulder skin when it was only a silver.
The fact that these skins are already expensive, despite the fact that I think they're not "super" hard to get at if you dedicate yourself to playing the april fool's event, shows that they are going to be worth a lot more when the supply starts drying up.