I inherited mine, so other than the maintenance cost of replacing bearings from time to time, price is/was not a factor for me. Knowing what I know from having mine for about ~4 years now, it is a better VALUE than dare I say, a KAPEX. Unless of course you happen to like emptying 1/2 of your truck so you can climb up and in to get to something against the bulkhead of the bed.
If/when you install one, see if you cant get something worked out to "smooth out" the sides/fenderwells. When I load mine, there is a 'little giant' type ladder on the left fender, and a home made case for rails & levels on the right. I make it a point to stack things that will catch (cords, hoses, random loose shoosh) on the right. This way if the cargo decides to shake loose any, the catchy things only have the smooth box to rub against. On the left side, I load 'smooth' things on the tray (read: systainers) so there is nothing to catch on the ladder.
The links to images posted up-thread are of units that appear to be of higher quality (sturdier) than mine. Mine also has a plastic pan/tub (whose shape is now somewhat distorted, no places for tie-downs, and (near-)zero potential for quality modification or bracketing.