Originally Posted by Kimmo

The reason 11s chains are more expensive is that they became too narrow for the normal bushing arrangement, where they're just punched from the side plate, which makes a radius that subtracts from the available bearing area. 11s chains have separate bushes pressed into the plates, providing more bearing area than a 10s chain, maybe more even than 9s.

Because the internal width is the same as 10s, 11s chains are a good upgrade for 10s bikes, offering extended chain life and less chain rub. Worth the extra $.