As a result of my efforts, I can now confidently share the following general guidelines on sealed MTG investing with you: Timing the market on the buying and selling of singles is more profitable than holding on to unlimited print run sealed product by a large margin, BUT you need to be good at both picking cards and timing the market
Note: These are unofficial fan-made proxies not affiliated with Wizards of the Coast
First, it only has a single printing and saw a massive price spike with the printing of Shelob, so it'll likely be the most expensive card in an otherwise budget-friendly deck
SA cards appear in approximately 20% of boxes (~1 in 5 boxes for any SA, ~4% per box for Mewtwo V SA specifically)
deck in its own designated area and shuffling their own main deck, then drawing five cards
People are also always trying to have the lowest price on eBay, which drives down prices, which while good for us buyers, can drive down the market value of a card