It’s fine. I understand why you would be skeptical. I studied metalsmithing in college, so I’m pulling from my knowledge of working with raw copper and applying/avoiding patinas. It has been my experience that raw copper items that touch your skin will develop oxides eventually.

Modern copper pipes don’t have that problem, because they’re often covered with a protective coating from the factory to protect against oxidation (which is why you have to sand joints before soldering, as I’m sure you’re familiar), and people rarely handle them after installation.

These buttons could be just fine and never develop a problematic patina, but I wouldn’t personally take that risk, because ≈$500 replacement cost is high for me. Even the example image shows the characteristic blue oxides, though that could be from an intentionally-induced patina for advertising purposes.