This forum and the Star forum are filled with messages about RTW trips, how to do them and their costs. Do some research in the various threads here and there.

Quick answer for OWE is from a few thousand US$ to about ten thousand US$ depending on the number of continents you travel (3-6), what class (economy, business, first) and where you start and end your trip. A well constructed trip in 4-6 continents can add up to 60-90,000 miles, give or take a few thousand.

There are also mileage based fare for both OW and Star. They generally have a much higher cost/mile traveled then a true continent based mileage run trip.