The 45-year-old "Hero" hitmaker recently got engaged to billionaire Packer and they won't be holding back when it comes to their big day, reported Female First.
"James is as big a diva as Mariah - he expects the royal treatment wherever he goes. He has promised her the most spectacular, over-the-top, wedding and told friends there's no budget. Mariah wants a summer wedding and has set up meetings with event planners and designers," a source said.
"Mariah is telling everyone to expect the most incredible and most expensive wedding imaginable.