The way MPC went about the entire Star Wars line was fascinating. There's not a hint of any sort of attempt to have a consistent scale among the vehicles. Examples (as per Scalemates):
- Vader's TIE was in 1/36, but Luke's X-Wing was in 1/43 and 1/63 for the ROTJ version; the standard Imperial TIE was in 1/51; TIE Interceptor in 1/51 then in 1/48
- Rebel Y-Wing was in 1/95; A-Wing in 1/48; B-Wing in 1/98; Snowspeeder in 1/22
- Imperial Shuttle Tydirium in 1/89; AT-AT in 1/100; AT-ST in 1/54; Speeder Bike in 1/11
- Boba Fett's Slave-1 in 1/85
- Threepio & Artoo in 1/8; Darth Vader in unknown scale
I'll put this down as a classic case of old-school model manufacturers basically making up scales out of thin air just so the parts trees will fit inside a pre-determined box size, in a way that was sort of typical in the store retail market of the first thirty or forty years of the kit industry (see also Revell's warships, ranging in scales from 1/429, 1/500, 1/700, 1/720, etc etc etc as another example of this sort of boxing) . Either that or AMT were under some sort of pressure from 20th Century Fox/Lucasfilm to have the finished kit be able to easily fit into a kids hand so they can chase each other around playing starfighter duel. They were probably correct in assuming things like "they're just kids playing with toys, they won't care in the slightest about accuracy in either scale or detail".