All his ex birds with kids are screwing him big time for cash, don't get me wrong he is making a better living than your average guy but he doesn't have that much cash to throw about. He can't even give his family money, they are all literal jakes with old clothes.
As for contracts, Celtic are a Europa cup team paying Champions League wages. For years they were winning the league by a country mile. Average players thought they were good, decent players thought they were great players, they asked for wages based on their delusions of grandeur and their board were happy to give them it.
But the problem was that they might be winning trophy after trophy, but this was based on the worlds biggest 1 horse race. They could have capped their wage bill to ¼ of what it ended up and still ran away with the domestic trophies year after year. And every now and again they would unearth a player like Van Dijk or Wanyamma to sell on and make the bank look good, but even that has stopped, none of their current players could fetch a tidy transfer fee nowadays.