Face is £60. It's a lot but he's only playing that one show
Well, SO FAR. If you look back at Moz's previous UK tour announcement history over the past few years, you will see a recurring pattern. A big show is initially announced as his 'only scheduled UK show' (Hop Farm Festival, Manchester MEN, etc) , to try and persuade everyone to panic and pony up the cash. Then, a few weeks later, more UK shows get added.
They won't have sold out yet. The 02 will just be releasing them in chunks, so they can make money selling them at inflated prices on Stub Hub. Keep checking, and stay calm. More will be released over the following weeks once they've sold as many to desperate folks at twice the price.