The Ditra adds 1/8 inch to the floor. It acts as a 'decoupler', allowing the subfloor to do things like swell and shrink, leaving the tile somewhat isolated from the movement. For this project it only added $160 to the overall cost (plus maybe a bit of extra thinset). The indentations are actually dovetailed, creating a lock between the thinset and the membrane.
The tile is 3/8 Bianca Gioia marble from good ol' Italy. Got it for under $8 a foot, plus got the guy in the warehouse to throw in an extra box (10 feet). Might buy a couple more boxes and do my basement bathroom to match, as I also have a bit of extra Ditra. Tile is being laid by someone I stumbled across who had done work for some friends. Not sure where Milan and I got disconnected after he came to see the work. This guy came highly recommended and was well versed with the heated floor and Ditra.
The wall is being trimmed out with beadboard, chair rail and baseboard. Got all the trim delivered from Central Fairbank lumber today. Total of 4 pieces of trim for the chair rail, 3/8 thick panels for the beadboard and 3 pieces of trim for the baseboard. My trim carpenter is going to hate me! But all the lengths of trim are long enough so there will be no mid-wall joints to worry about. It's all getting primed over the next few days on all faces to help with moisture.