I just did a quick look at 11 spd parts
seems that chains are just a bit more than 9, 10 spd,
some cassettes though are pricey, from 100-200-300 clams each
here's a question--does 11 spd stuff chains, etc, last a LOT less than 9 spd stuff?
We only have one 10 spd bike in the family, so dont even have that experience yet, not replaced the chain yet.
Ive generally gotten about 5000kms out of 9 spd chains, similar or a bit more for 8 spd, similar or a bit more for 7 spd---but of course, drivetrain cleaning, maintenance, how you ride, how strong you are, how heavy you are, ---- ALL play a huge factor in this
-how much does chain angle affect chain life--although Im sure chain condition, ie clean or not, plays a big part here too.
and to finish, I still see my triple 9 or 10 spd as the perfect setup for touring WITH A GOOD LOAD. Mid ring for most of riding, large ring for downhills tailwinds, and granny for climbing.
I use all speeds in back regularly, I use all three chainrings regularly (but not changing chainrings so often its a pain in the rear)
the cost of replacement stuff is not expensive
the few extra pounds (if that) of an extra cable, fd, fd shifter and two more chainrings IN MY CASE, being a light little bugger, is nothing....especially nothing compared to how I use my bike, ie loaded up for long trips, carrying extra food, water etc