first of all... you cannot be absolutelly sure and say that a certain product is cheap to manufacture unless you are working for the company that produces it.
there are various processes behind the scene that we, the customers don't see. I'm talking about materials supply, supplier and manufacturer location (worldwide), supply cost and method, raw material processing, patents, manufacturing, worldwide distribution and so on and so on...
now on the discontinue question...as you know the market dictates the rules. you can have a good product, but it has either to be refreshed or new products must be added to the product range IF YOU WANT TO STAY ON TOP! Else you fall behind. the market is fastidious and vagarious. Customers require fresh new ideas to keep their attention on.
so finally you as a manufacturer must decide to refresh or to make something new. and it is realy rare when you can have both.
if the product is old and the current technology allows you to produce something better, that will sell beter...you go for the new thing.
Imagine another problem...your subcontractor or supplier bankrupt and ...then...the new ones cannot supply the same materials at the same quality...thus you will compromise the quality level for your time proven product...then what... you discontinue it.
BUT...one big BUT! this is only what i think and not being involved in any real production process (my knowledge is theoretical...please don't kill me, i'm open to positive criticism) i might be wrong about the reasons for "discontinue" decision.
last...and i shut up.

)) Secondary market is always an option...I'm really angry that such does not exist where i live....
good luck searching
