To be fair, while Lucas and co. definitely skimped on the sets, they more than made up for it in the visual effects. ROTJ was never really topped in that department until Independence Day came out a decade and a half later, with digital technology to boot. It was a spectacular film, but for different reasons than ANH and ESB, which had great locations and more than a few incredible sets. Of course, ESB still is the highpoint of the visuals, with great sets, locations and photography (Hoth, Carbon Freezing, Dagobah) as well as great visual effects sequences (Imperial Walkers and asteroid chase).