It appears that the lowest base prices for business class Star RTWs originating in Europe are those that start and end in Norway. For example, a CRWSPCL RTW (26,000 flown miles max, some stopover limitations) originating in Oslo has a base price of €5436 (taxes and airline fees additional, depending on airlines used and stopover points.) That would allow a route of, say, OSL-FRA-SFO-AKL-SYD-SIN-FRA-OSL (25,276 miles.) The same ticket ex-AMS would have a base price of €6093.

A CRWSTAR1 ticket (29,000 flown miles) ex-OSL would have a base price of €5855 and would allow you to add additional stopover points (Vancouver? Hawaii?) to the route.

You can see base fares using Expert Flyer (subscription service) as they can't be advertised due to taxes and fees being so variable depending on airlines and specific routing. Most countries and the EU require that advertised airfares be inclusive of taxes and fees, which is impractical with RTWs.