Metal is still cheap compared to new equipment, though not by the same margin. Much of Gingery's machines use cast aluminum, which is something that can often be found for free with enough patience - melt down soda cans, broken transmission housings if you have a mechanic friend, old furniture if you can find an office going out of business, etc.

Even at the time, you were probably better off buying a machine if you wanted one. However the learning experience of making your own is very valuable. The deep understanding of how the machines work, combined with practice means you are more likely to be able to use them correctly once you have one. (if you finish of course, most people don't)

While I wouldn't recommend a gingery lathe, I don't see any reason to ignore an injection molding machine design that is small, known working, and simple to the point of being obvious. You can certainly build one faster than you could find a castoff on Craigslist, and unless your shop is quite large you may wish you'd built the smaller machine even once you got your used industrial one working.