Bono could cost U2 €120m.
The singer has been told by doctors to rest for two months following emergency back surgery and will now miss out on the start of the group's US leg of their 360 Degree tour.
Bono was said to be "heartbroken" after pulling out of 17 US dates and Glastonbury festival in the UK, and now the problem may hit his bank balance too.
A source told The Sun newspaper: "Bono and the band are covered by insurance but the cost of overheads and missed revenue could easily reach £100m by the time he's fit enough to perform again."
Paul McGuinness, the manager of the Irish group - made up of Bono, The Edge, Adam Clayton and Larry Mullen Jr. - said: "If we play or not, touring still costs us £500,000 a day."
Earlier this month bassist Adam Clayton admitted he and his bandmates would have been happy to put on a simpler tour, but Bono had other plans.
He said: "It was Bono's vision. He's that kind of performer. I think the rest of us would be happy to stand on an old beer crate but he's the person working the stage."
New tour dates are expected to be released later this week.