What you are buying is three separate pieces here that are welded together... not one solid rail piece. True, this is a cheaper option than purchasing the pieces individually, but the welds that held it together were ugly and weak.
The friend I had installing these wasn't comfortable using their welds, and ended up rewelding the pieces on both sets of frame rails (I purchased the driver and passenger side full rails). It ended up costing me another $300+ in additional fabrication.
If you are able to weld and can fix them yourself, it probably isn't a big deal, but if you have to pay someone to do it for you, be prepared to either have poor welds or paying extra to have them 'fixed' so they will last.