How do you feel about driving yourself from HND to NRT? Should be possible to rent a large enough vehicle for significantly less than $500.

For express transportation there's Akabo ("Red cap" - basically a man with small truck). I think it might cost around $200 but would be challenging to arrange unless you speak Japanese -
https://www.akabou.jp/person/fare/shutoken/#jikan.

This small truck delivery service has an English site - You could ask them if they can do a timed delivery for you
Tokyo Happy Move Delivery Company in Tokyo. Cheap and English Speaking

I wonder how much it would cost you to ship your skis / board from Hokkaido back to Boston

If you decide to do the 9 hour layover at NRT, you could go into Tokyo rather than going airside for all that time.