My February 1978 Leica system catalog price list has the following:
55E circular polarizer $177
Leicaflex motor $1,650
Noctilux f/1 $960
and lastly, an
M4-2 $993
Adjusted for inflation, in 2011 dollars they would cost:
* 55E circular polarizer $614
* Leicaflex motor $5,725
* Noctilux f/1 $3,330
* M4-2 $3,445
Only the Noctilux made it--it's currently selling for ~$6500 despite the f0.95. During those times, the future of Leica was even more uncertain than it was during a few years ago.
From an investment standpoint: the Notilux has grown 580% in nominal dollars (and double in real dollars). By comparison, the SP500 returned ~1200% in (nominal dollars) over the same period. That is without dividends reinvested.
Moral of the story: Leica gears don't go down in price. A $1,000 M4 from 30 years ago still sells for $1,000 today. However, inflation will eat away much of the value.