This topic touches on the general subject of the sweet spot of cost/value/performance for any given gearing system.
Go back a few years and it was clearly 9 speed. Now with 10 speed coming on a bike like a lht, and the cost of ten stuff being less, I'd go 10 for a bike being used in a lot of places.

So part of this discussion will always be a mix of performance, cost and longevity, and 11 speed is clearly new, so will be more expensive when you take all the parts into account.