I've seen that TT mount on another bike and it looked pretty dang solid, though I can't say how it compares to other $200 options. I have Givi racks on my 2012 and Seahorse brand cases. I couldn't bring myself to spend that kind of money on brackets and so after staring at the cases in the living room for two weeks (my girlfriend was very understanding...) I rigged them up with a homemade set up based on stuff I saw online.
The bottom part is made from two 1.5 x 6" 1/8 steal mending plates with a U shaped slot to fit with the lower "buttons" on the Givi rack. They are spaced out with pieces of a white nylon cutting board and bolted with SS bolts and locknuts, fender washers, rubber washers, etc.
The top attachment point is kinda quick release. I removed the Givi latch point. I ran 1 quarter inch SS bolt and a clevis pin through the holes in the Givi rack and jammed a pair of rubber bumpers over them to space the cases out and seal out rain. The bolt and clevis pass through holes in the case. I use a wing nut and fender washer on the bolt to tighten the case back to the rack, then slide a hairpin cotter pin into the clevis pin to lock it. When the cases are locked there is no way to remove them from the outside. It only takes a moment to pull that cotter pin and spin the wing nut off to pop them off the bike when I want to though.
I'm sure my setup is not entirely new but I'll take a couple pictures later today if anyone is interested. Once I actually started working on them it didn't take very long to put it all together.