I have two bikes with 11-speed drivetrains, and exclusively use the SRAM PC-1110 chain, which is the cheapest 11-speed chain on the market. On Amazon they are typically $14-15.

I wax dip my chains, so I buy two at a time (so it's roughly the same cost as buying a single 11-speed chain of "higher quality," and rotate the chains throughout their lives. Pairs last 5,800-6,500 miles depending on conditions.

In the past for 11-speed I have tried: SRAM PC-1130, SRAM PC-1150, SRAM PC-X1, Shimano HG-CN701, KMC X11-93

Interesting to note that Bike Rumor posted a test where the Connex/Wipperman 11SX lasted over 3x as long as the PC-1110 in their tests. Would be neat to find out, but for the price of one 11SX, I can get five PC-1110s.

I somehow doubt a 11SX would last 15,000+ miles under even the best conditions.