Most affordable or best value of the islands?

My partner and I are currently traveling in NZ. We are making loose plans to head to one of the pacific islands and we are looking for your advice. We want to know your opinions on what island you would consider the best value or the most affordable. Along with the economic aspect we would like a cultural experience and don't mind roughing it or spending for the proper place. We are three months deep into our open ended travel and I have a wild hair to head to the Cook Islands and get a ukulele ( from an article in the NZ Hearld). We have looked into becoming crew for yachts or hitching a ride on a cargo freighter and that seemed to work circa 1997. So with that said, we will only want to splurge on one airfare (well 4) which limits us. If y'all know of any WWOOFing or volunteering positions we are open to those. Hell, if you know of work on any of the US or NZ islands we are available, she works in graphic design/marketing, I work in ecological restoration. We are open to spending a good amount of time on the proper opportunity.

Without doubt, "the best value or the most affordable" country in this region is Fiji.

However Fiji, along with the Polynesian countries, is rather homogenous culturally, so if you are seriously looking for the most diverse "cultural experience", the other Melanesian countries are better - PNG has by far the most diverse cultures, followed by Vanuatu and the Solomons.
They are more expensive than Fiji though.

Don't plan on finding paid work in the islands - if you want to earn money, do it in NZ or AU.

There are a number of environmental projects in Solomon Islands that might be interested in volunteers. The best clearing house for various NGOs is the Development Services Exchange in Chinatown, Honiara.

If y'all know of any WWOOFing or volunteering positions we are open to those.

WWOOFing in Samoa is available at www.wwoofsamoa.com. Volunteering in Samoa is also available at www.swapsamoa.com.