attached to a piece of plain cardstock or in a paper envelope

I figured that since obviously you wouldn't be mailing a pin attached to a piece of cardstock without then putting that in a shipping envelope and I used the word "or", it would be obvious that I intended the same for that. I was referring to this sort of paper envelope.

I'm sure some customers keep the packaging, but I assure you that the overwhelming majority do not. I'm not saying you shouldn't package your pins so nicely, but that it would be nice to have an option to elect for minimal packaging - just the bare minimums to assure safe transport. I never mentioned eco-friendly materials, but rather low-waste packaging, which is an entirely different concept and something you can achieve by using less of what you already have, not by buying different packaging materials.

I'm glad you take pride in your work, but the reality is that almost all of the packaging is going to end up in a landfill. Most customers won't even recycle it. By offering a low-waste packaging option that costs you no more to do, you can potentially reduce the impact ever so slightly. Yes, there are much bigger fish to fry out there and this was never meant as an attack on your business - everyone here is just being far too defensive. That doesn't change the reality though that when a difference can be made, no matter how small, it is worthwhile to consider pursuing it.