U2's dazzling stage set-up, dubbed by lead singer Bono as the "spaceship." (File photo)

Rock giants U2 are still to pull in a profit from their sold-out 360* world tour - because the mammoth show's overheads are so costly.

The Beautiful Day legends have been on the road since June, rigging a huge steel construction, dubbed The Claw, as their portable stage.

But constructing the giant sculpture at every new venue, plus paying the huge team needed to put it together, doesn't come cheap - costing a staggering $750,000 per show.

And despite selling out tickets around the world, the group won't actually start pulling any revenue back in until the North American leg finishes next month - despite being on the road for three months.

U2 manager Paul McGuinness explains, "The tour's engineering problems are enormous and costly. We had to find a way for it to be aesthetic and figure out a way of doing video.

"Whether we're playing or not, the overhead is about $750,000 daily. That's just to have the crew on payroll, to rent the trucks, all that. There's about 200 trucks.

"Each stage is 37 trucks, so you're up to nearly 120 there. And then the universal production is another 50-odd trucks, and there are merchandise trucks and catering trucks."