The Naish is a tri fin, but the Cabrinha is a quad with 4 powerbox fins and costs £999 and is 183 by 58.5cm.
The Fanatic quad windsurf board 2011, is 226 by 53.5cm, has the same number of fins, deckpads, straps, and has one thing extra (apart from the extra size) - a mast track, and it costs £1489. Thats a more expensive construction, but based on their Skate, even in the cheaper construction it would be about £1229.
http://www.roho.co.uk/acatalog/Fanatic_ ... oards.html