Hi Phoenix
While I'm not familiar with the Disco indicator stalk, I am imagining it is relatively complex. 3 position and a return mechanism for the indicators, 3 positions for high low beam and instantaneous to flash the high beam and probably also horn button so a 7 function switch in 3 planes.
The interior lamp switch is a simple two position, single pole rocker switch. As far as I am aware it was used on all 90's 110, 120, plus Defender 90, 110 and 130 for at least a decade or fifteen years. There is little technology in it, no circuit boards, not even an indicator lamp, it is a simple switch that can't justify the price.
If my Land Rover specialist was making a huge margin on the parts, why are none of the other 7 perentie parts not more expensive than $17.00.
Diana