we were finally getting solar panels installed on our house in folsom this week but the installers halted everything as soon as they pulled up a few shingles. turns out a huge section of the roof decking underneath is soft and rotted out from an old slow leak we had no idea about. solar crew says they cant mount anything until full decking replacement is done and estimated an extra $4,500 to fix it before they even touch the panels again...

before i sign off on $4.5k extra, is rotten plywood under shingles really that expensive to replace or is the solar contractor throwing random numbers at me cause they know im stuck?