My guess is that the $59 81-1011 is for the 96-99 W140 and the $249 81-4011 is for the 92-95 W140. The 81-1011 is also listed for the W210 which shares mirror parts with the later W140.

It might work out cheaper for you to update your car to 96-99 mirrors on both sides.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD