$30 for the cold brew machine seem reasonable, but I’ve been pouring coffee in plastic bottles to make my cold brew. $0, I don’t even filter it as it just deposits at the bottom, but I don’t know whether the machine is somehow better.
I've found using a french-press with luke-warm water for about 12 hours works great. Probably not as strong as the cold-brew machine, but perfectly fine for my needs in the summer time.
I can safely say that my investment has amortized down to something very close to $0...