I have priced it out to $2.30/L for C-41 and $1.90/L for ECN-2. Of course it also means hundreds of dollars in equipment as well, even if you go the cheap route. At this point I have spent enough that I probably could have bought enough chemicals for a year of developing and saved myself the headache as well. So is it cheaper? Yes and no. And that's with the caveat that my C-41 is still not quite performing at the level I'd like. It outperforms the powder from cinestill in overall color balance but still lacks the punchiness in the reds and greens. That being said, I think home brewing is worth it if you are consistently developing ECN-2. It's cheaper, has less ingredients and I consistently get good results from the published EK recipe.
C-41 has proved more complicated, at least for me. My V4 (with the potassium iodide included this time) is certainly acceptable for use but creates a noticeably cooler tone when compared directly to the factory chems I have available. Still ironing that discrepancy out, although a cooler tone could be desirable depending on what you find to be your "ideal" image.
Other than an expensive pH meter that I chafe at and probably would not buy, I believe I have everything else that I need. So I don't think it would cost me hundreds, it would only cost me whatever I pay for a less expensive pH meter and calibration solutions, and the chemicals. I've never shot ECN and have no plans to. Since (what I consider) decent C-41 costs $30/liter, and only develops 8 rolls of 120 without reuse, and I don't reuse, anything under 10-15 bucks is quite attractive for DIY. $2.30 would be a dream! I could actually start shooting a lot again.
But it has to work as well as good commercial product, or it doesn't "make sense." Never tried Cinestill or any of the "off brands" because I don't trust them. Unless UNicolor is considered an "off brand."
Anyway I don't want to derail your thread and I hope you solve your issues, as that would be encouraging to me.