This was more or less the plan behind the original Ponzi scheme. The problem is that it’s difficult, if not impossible, to convert stamps back to cash at anything close to face value.
I once sued because the jail was selling Forever stamps at 49c but Congress had reduced the price to 47c. The government's argument was that they had purchased 10,000 of them at 49c, so selling them at 49c was legal as they weren't "ripping anyone off." The appellate courts did not agree with that argument.
Also, funny thing in jails, the sticky leftover gutter parts of the stamp books had value because they could be used to repair torn things like books, photos and magazines.