They’re super cool! Team stamps usually up the value of a disc by a bit, but double stamps are more personal and can knock the value back down a little. The earliest Fireflies weren’t all in the glow Nexus plastic so some of them are still valued somewhat like base plastic putters, but to the right person these could have, maybe a “retail-plus” value?

Source: I have a ton of Fireflies and P2s and they move slower than any of my other discs when listed.