http://www.espn.com/nba/story/_/id/22420673/cavaliers-face-300-million-dollar-future-espnSo in the piece, ESPN outlines what will happen if Cleveland re-signs Hood at 12 million and Lebron comes back this summer (they used his option salary amount of 35.6). Along with the BKN pick (they used the 7th pick for salary) and free agent minimums to fill out the roster, the Cavs payroll would be 158.9 million (and that might be under selling the real cost). However, since Cleveland will be paying the repeater tax for the first time, it will pay 149.2 million in luxury tax on that salary for a total payroll of 308.1 million.
The Cavs were the only team that lost money last year, they will almost certainly lose money this year (190 million salary when accounting for the tax), and will basically write a luxury tax bill that will all be a loss next year in that scenario. That isn't to say Gilbert won't do it or won't be able to find way to reduce some salary, but that is an insane proposition for any team. It is also what Golden State faces in 2020, and why that team likely won't stay together forever.
This is why, the Celtics will do everything in their power to avoid paying the luxury tax this summer. The longer you can avoid it, the longer it takes to get to the repeater tax zone, and the longer you can keep your core team together.