Cost - $3 for the two 1" stainless steel bolts I purchased. Time - about 4 hours start to finish.
Rest of the stuff was in the FIL's shop. He didn't have bolts with threads long enough for the top to just lop off the head, so he took some with partial threading, cut off the head and threaded the remainder on his metal lathe rather than go to the hardware store and buy to bolts with threading long enough.
You'd have to see it to believe it, but his shop has every nut, bolt, washer, lock washer (both standard and metric), key blank (he's a licensed locksmith as a side hobby), lubricant, tool, etc. known to man (almost). He's got table saws, band saws and lathes for both wood and metal and a couple of welding machines. We won't even start on all the electronic test equipment he's got! Best thing about all the rooms in his shop - he's got everything, and I mean everything cataloged and coded for location! Yes - he's been retired for about 20 years now. All four of us son's in law still have trouble keeping up with his energy and he's got us all by more years than we care to admit!
My father in law had been given a small hunk of billet aluminum that he just had laying around his shop that was a perfect width. He also had the necessary tools to cut, mill and tap the aluminum. Had a lot of fun learning the use of the milling machine and working with him. He's a brilliant man that loves everything tools. He reads tech manuals for fun and at 86 is as energetic and sharp as I've ever known him in the 25 years I've been married to his oldest daughter!
Haven't a clue what something like this would cost to lay out on a CNC machine and have professionally milled. A one off would probably be quite expensive, but a run of 10 or 20 probably not as bad. Mo and I had tossed around the idea of doing this and selling here on Mud, but he's moved on from his metal shop and I don't have the interest in really pursuing it. He had a contact that could mill the aluminum.