Now I'm imaging some sort of push on r/wallstreetbets to YOLO on stamps, posting insane strategies on how to predict when the price of postage will go up, by how much, and how liquid the market is for millions of stamps.
For a cash-like instrument, stamps seem to have very little in the way of anti-counterfeiting security.
It goes like Ebay says spend $X or sell $X on ebay and they'll give you a rebate. (Or sometimes the rebate comes from a credit card or Bing). If the $X covers ebay fees and shipping, then buy stamps to reach the $X and then sell them when you get them. If the rebate it sufficient, you can sell the stamps for less than cost, because you're already ahead.
From elsewhere: “With low interest rates continuing to reduce the Bonus Bonds prize pool, the Bonus Bonds scheme was closed to new investment on 25 August 2020 and an announcement was made that ANZIS intended to begin winding up the scheme no later than the end of October 2020.”