Curiosity having got the better of me, I thought I'd see if I could find the earliest reference to "economy cooking" in historical newspapers, just to show how old the concept is. Haven't pinned it down yet, but by bizarre coincidence, it did turn up this from the
Dorset County Chronicle & Somersetshire Gazette of 14 September 1843, advertising "E BROWN'S UNIVERSAL COOKING APPARATUS AUTOMATON ROASTING JACK." All the more remarkable given that I obviously didn't include "Jack" as a search term.
"The Roasting Jack revolves as soon as placed before the fire, without the aid of weights or springs, and is not easily put out of repair."
Every home should have one.