It's why I keep my '48 Mercury convertible registered in New York. When I got it, I showed the bill of sale and paid the 4% plus local because I wanted regular plates. It's parked in a garage, so D.C. doesn't really say much about what they don't see. I drive it up to NY enough that I usually can get it inspected. If not, New York does allow you to go late if the car is out of state when inspection's due. It's registered to a relative's address.

I asked about registering it in D.C. and like OP says, they go on the NADA value. Mine is close to it, so I'd pay a lot. They don't make any allowance for it being a basket case. or a rust bucket. I had a friend who bought a '64 Caddy rust bucket and they wanted thousands of dollars to register it with regular plates. He got WVA plates, instead.

D.C.'s pretty bad about it and totally not flexible.