If you already have a power rack with low/high pulley attachment and need a cable cross over, then you need to spend only about 30-50$ to get this system. I have used it for the past one month (6 days/week) and surprisingly is very smooth and effective. I work with my friend who is quite serious bodybuilder (20+ years of experience) at the beginning he wasn't convinced but after the first use he loved it. We have done tons of exercises like cable cross over, cable chest press, flat cable fly, shoulder press, plus many other exercise that you can do with two dumbbells. There are a few things to consider:
1- The cables are narrow: compared to the conventional cable cross over, I actually found this an advantage, with this I can do chest press, also the fly movement is sufficient and lighter on the shoulders. I'm 5,9 and its comfortable for me, my brother is about 6,1 and he also felt okey with the fly movements.
2- Attaching the cables to the rack: attach the pulleys to the rack let them hang loosely, this way the movement of the cable is very smooth without any noise.
3- Weights: with the conventional cable cross over there are two separate weight stacks, with this system there is only one, I partially solved this disadvantage by using a single cable which goes through a pulley. Attachment of the system to the low or high cable (yellow arrows) can be with one cable from each upper or lower pulleys (blue arrows) if this is the case then when you are doing your exercise one hand can help the other, but with the current system the two upper or lower pulleys are attached by a single pulley which allows the cable freely move, in this arrangement each hand gets the same load.
3- Safety: its safe. To be sure of the safety use steel cable and pulleys strong enough for the weights you will be using. To make a ring at the end of the cable I used U shaped grips which have bolts, I used two each side for extra safety.
4- The set up is very easy to make, it took me less than 15 minutes to make it. Once you made it, it takes less than 15 seconds to instal it on the rack.
I hope this is useful. I wish I had done this 2 years ago when I got my rack.