surf boarding is a hugely popular activity where I am from. (San Diego, CA). And there is plenty of business opportunities in the nice niche market. I think the value of the keywords is obviously well known, the question begs how does this TLD effect value?
The answer is simple, lets review some sales comps from the .biz extension. Based on some of the recent Sedo sales, I think you may have found a decent .biz domain name. Because of the niche market, your probably looking at around $30 - 75 dollars for resale... You could get lucky and hit an end-user, but I think its a longshot to do more than $400
Good luck,
Justin