That's interesting Jack. Certainly not very portable. I bet it takes them hours to unload them from their vehicles and set them up. I guess if you live in a castle, were you could have them setup permanently on the battlements, they could be practical.
Somehow when I was watching the video, I started imagining these gentlemen setting their rifles with wind correction, drop, et al. Making sure the table is stable and level......just like we do!
Then there's all the precision machining to get every last measure of performance knowing perfection is but the goal.
Back in '75 or so, I spent what I thought was a fortune on a Browning over/under. Had custom engraving and gold plating. Think I paid around $3500 for it.