Honestly, that math never works out for me. I tried the dried bean thing last month and the gas to simmer them for hours probably cost more than the canned kind. My time has value too, and after a ten hour shift I'm not chopping onions to save a couple bucks. Sometimes the pre-made stuff is just the better deal.
Right there with you. I tried dried chickpeas once, spent an hour soaking and then they were still crunchy after two hours of boiling. Ended up ordering pizza that night anyway. Pretty sure the electric bill from running the stove that long ate up the difference.