The business end of any current JP1 cable is the USB part with all the electronics that do the serial communications. That chip and associated circuitry is the expensive and complicated part. The $3-$5 Nokia cable has this chip, but the wiring is all wrong for JP1, and there are only 3 wires in the cable, which is fine for a Nokia phone, but not enough for a JP1 remote. So you have to open it up, remove the current cable, solder on your own 4-conductor cable and connect your own 6-pin connector (2 rows of 3 holes). I posted a lot of detail in a big thread on the JP1 site with pin-outs and pictures that was eventually written up in a PDF by Tommy Tyler, our resident JP1 cable guru. Although it's the cheapest solution, it's not the best because it's somewhat hard to find and build, and the drivers are hard to find because it uses a counterfeit chip that won't work with the official Prolific drivers. But if you want the cheapest possible solution, it works.
You're correct that any pair of 3-pin connectors will work. I used the CD cables as an example. I've also used old IDE cables cut to size, and other similar ribbon cables. You can use anything you want, so long as it has 4 wires and fits the JP1 plug.
The $12 FTDI cable is by far the best DIY solution because it has the best chip, requires no driver download (comes with windows), and requires no soldering or new cabling. All it requires is a 2x3 connector. In the procedure I linked earlier, the guy simply cut that long single row connector in half and glued the halves back to back to get the 2 rows he needed. You could just buy the correct connector, but shipping costs usually make that too expensive.
It's complicated because there are so many options. Not long ago, the few people who made these cables had to buy the USB-Serial chips for $20 or more, solder in all the other tiny parts by hand, and connect and terminate the cable and try to make a little profit. Hence, a good cable was at least $30. Enter some of these cheap Chinese cables with all the circuitry already there. Now it's just a matter of making the right connections for JP1. There are lots of different cables and lots of different options.
There's no law that says you have to make a cable. If you spend enough, you can buy one ready-made. But if you're a cheapskate and an electronics hobbyist like me, then making your own cable is kind of rewarding.