Just like trump said, the ballroom will cost $100 million and all $200 million of it will be privately funded. Taxpayers won't pay a cent of the $300 million because all $400 million of it will come from donations. Only $1 billion will have to come from the taxpayers.
I just want to point out....
The amount of money the United States has spent on war in the last 67 days, is roughly the same cost that Bernie Sanders proposed for universal college. So the real question is never can we afford it, it's what we choose to prioritize.