Surfboards and Surf Memorbilia can be hard to price actually.
I've been to see a few of Mick Mock's auctions that he helped organise.
I'll never forget seeing a bidding war on a Surf Pinball Machine. Felt like $1,000 tops, but Damien Hardman finally won with a bid of Five Grand. Mind you, he was shaking his head and laughing at the absurd price... I guess $5k didn't bother the Hardman too much!

Speaking of Hardman, I used to see him around here a bit with his job a RipCurl. Maybe he doesn't need to get down here as much anymore. He loves Winki like the rest of us Speed Freaks!!
Edit- that was bang on 10 years ago, and $5 Gorillas would be equal to about $8k now.