Even cheaper.
I use 1/2" masking tape and fold it over the wire. I write on it with a sharpie.
Works really well.
Ugh. World really well...for how long? Masking tape gets funky over the years: dries out & gets crumbly, gets gooey & yucky, Sharpie or ball-point pen bleeds/fades/spreads, etc. I used to use masking tape & pen for all sorts of labeling, but no more!
For my home entertainment system, I got a fancy smart strip (receiver is master, TV & a few other things are slaves...I think it's a Rocketfish(?)) It came with a sticker sheet to label power cords. Awesome. My Onkyo receiver also came with a sticker sheet for speaker wires & inputs. Also awesome.
On both of these sheets, there was plenty of margin around the pre-printed stickers for me to Sharpie my own text & then cut out a rectangle & wrap it around a cable. Again, awesome.
For my arcade cabinet, labels were key, as I have so very many USB things inside & I needed to remove the CP from the cab to get it out of my old home. Setting it back up in the new place was a breeze. I used a P-touch label maker for all of the important cables in my cab. Once more, awesome.
Thanks,
-Jason
PS--for my I-PAC, I took a photo of my control panel, pasted it into PowerPoint, overlaid the keystroke for each switch, noted the I-PAC terminal block location for that switch's wire, printed it out on big ledger-sized paper, & tucked it into my cab's coin box.