I did a similar experiment some time ago comparing a 1950's Agfa Sillette with an Apotar lens with a Leica M5 and Summicron.
Under street conditions - hand held, no time for critical focus, smallish f-stops for depth of field, only the center of the image holds interest - there was little difference between the two.
To see a real difference the cameras had to be tripod mounted, working at their best apertures and critically focused. Even then in the center the difference wasn't worth a whole lot and certainly not worth the spread between $20 and $2000. In the corners the Agfa was pretty miserable until f11 at which time the center was beginning to suffer. But if you are going to be carrying a tripod and doing a whole critical-this-and-critical-that slog why not use a 4x5 and do a proper job of it - there is no substitute for square inches of negative.
Of course, you don't get no respect with a Sillette.