They surely look nice, and that looks like gold plating. The problem is, the clips might be brass (most likely) or steel underneath. My experience is that these are pretty much never copper. I have a box of nice-looking inexpensive connectors from multiple suppliers that are gold plated and claim to be copper, but have only found two suppliers of plated copper connectors. You have to grind off a bit of the plating to see the color of the metal underneath.
Some of them are pot metal - a cheap zinc alloy.