The market was completely different. Home collectors were a minuscule part of the equation. Bally/WMS sold thousands of pins to distributors and was able to command high minimum orders from the distributors, especially after TAF which earned like gangbusters on route. So they were able to then ship thousands of TZ which did not earn on route. It was too complicated. How limited a machine might be in quantity was never a factor to anyone. The only factor was "will people put their quarters in this?" Now Bally/Williams/Gottlieb are dead and the info home collectors giving their old pins a loving home is readily available.

Stern (as with anyone else still making pinballs) serves a niche of home collectors and a much lower pool of operators today. Resale value among private buyers was never a consideration in 1993, but it is now and it may be why they don't disclose anything they don't need to.