We do a run of 250 similar badges for a non-tech convention every year. ~$10 per badge is about right all in. We've also done runs without ICs (just LEDs, a switch, and button cell battery) for about ~$4 some years.

That's awesome! I'm really happy to see non-tech conventions running badges. It's so cool that with today's technology you truly can "just make things".

What does your badge do? I'd love to see it!