If someone has a machine just sitting around gathering dust, why wouldn't they take on a job that might turn into something else later? There are a lot of ways to make such a simple part. The material cost could vary wildly also. I have a place nearby that I can get CRS and HRP steel by the pound dirt cheap. I have to go get it myself and it is in short lengths, but it is much cheaper that way. Labor costs can also vary. If you are only running a CNC, and depending on that machine to make you money, then maybe you need to make $50/hr for every hour it runs. But if you are only walking over to the machine every few minutes and removing parts and replacing steel, then do you really NEED to make $50 for every hour that it runs? If you can run 2 machines at once do you need to make $100/hr, 3 machines $150/hr? I believe this is how the labor cost is being reduced to almost nothing.
A good operator can keep at least 2 machines running, and with longer cycle times, maybe 3 or 4. With very complicated parts, you can do multiple setups and run with the lights out and the heat turned off, and come in the next morning and have finished parts waiting for you.
With all that being said, there is a limit to just how low you can go, and when you get busy, you can't turn down the good paying jobs for the charity work. I think that is why you see all these same small jobs coming back for re-quote over and over again. Also, some shops specialize in doing just this kind of work, they have the necessary tooling and equipment that is meant to do this kind of short-run work at dirt cheap prices.
That's just my $0.02 worth. I'm not trying to get in the middle of anything, just discussing the current state of the industry.
BTW: I didn't quote this job at all, it's too cheap for me, even with the lights turned off.