We were running at about 850 ft/min max but I suspect that they are much faster now. Yes, the systems are expensive but the price of the product printed justified the cost. I have no idea about the costs today but I suspect it has come down. It seems the systems are relatively smaller now.
To prevent x-ray exposure, the EB system is covered with lead and the path of the web through the system is not straight, so the rays can not get out. I don't think there are any EB units for sheetfed presses for this need to contain x-rays. There were also detectors that measured if x-rays were getting out.
These systems also required a nitrogen gas knife to blow oxygen off of the web surface because oxygen there affects cure. So large liquid nitrogen tanks were on site.