My thoughts: the last thing RW needs is an "economy".
The game is about building and surviving- not making money.
An economy, and corresponding "money" or monetary system, has been discussed for years in that "other" game, and several people have tried setting up their own.
The Barter System will always win out.
The only "economy" in a game like this that I've ever seen that has worked (some) is the one in Total Miner. In that game everything has both a buying and selling price (in gold coins) at the Store, therefore for RW, you'd have to put a buying & selling price on everything- from dirt to all the finished products. The proper balancing of those prices would take... a long time. Which would be for naught, as players could set their own "prices" each time they barter with another player. And in single player, it's always cheaper to make it yourself than buy it.