Its more expensive than hardibacker per sheet, but is twice as big, one 10mm wedi is cheaper than 2 hardibacker boards for me but we all use different suppliers, Gazebo, I cut out an access hole in the wedi and make an access panel from the tiles.
Wedi for me is cheaper and much much easier, very light, can be cut with a stanley knife.
It takes about 10 minutes for me to get it in the house, cut to size and put in place, I couldnt do one from hardibacker or cement board that quick.