To help answer hexidismal's original question, it is the nature of the "surplus" market that things start out cheap and then become non-existent or very expensive.
Now the FAL mags have been on the market for some years. This includes L1A1 magazines. As the various countries put their surplus arms and accessories up for bid and disposal, many of these items find their way to our shores and are then advertised by distributors. Depending on supply and demand, some things start in great quantity and a correspondingly reasonable price. Things in the market change and sometimes their demand heats up.
Even if that is not necessarily the case, eventually stores get distributed to smaller buyers and those items either get consumed as in the case of ammo, or they go into hiding as part of a collectors stash.
These things can go in waves or cycles like any consumer commodity. Before anyone had envisioned a semi automatic Bren gun, those kits were dirt cheap and plentiful. But as ingenious folks started to realize they could make them into reborn rifles, the demand for all things Bren started to heat up. I recall for quite a few years, IMA used to offer Bren tripods, at a very reasonable $100 dollars or so (maybe less in earlier days before I became aware of them). Well, once the 1919 semi auto and even Bren semi autos (to a much lesser degree) started to appear, the tripods became a hot commodity after YEARS of being very reasonable. I bet now you can't touch one for under $500. That is when the game is on. Now the hunt is to find someone who doesn't realize what they have and sells it off at a garage sale for $40 bucks.
But it is tedious work to find those single units that have been squirreled away by the individual collector, who may have passed away and along with him, the knowledge of what he has and what its worth is. For the rest of us "collectors" there are trades and sales among the learned, but not usually great deals!
Hindsight is always with 20 year old eyes.
