MINT 1970 Plymouth Duster Gas Cap in Plum Crazy Purple?

There's lots listed on Ebay for $100-$200. There's also lots listed for $25 that are just as nice. Listed price does not mean that they're selling for that much, only that someone's fishing the market.
If you're convinced you can get that much, go ahead and list it- no need to ask our opinions. Maybe you'll be extremely lucky. Don't be surprised if you aren't.