Surprisingly, this turns out to be a huge lie.
I had wondered about this because I knew that Trump put just over $50 million into his primary campaign. He's also given a million or two each month in the general - I think as contribution matches. That would still leave him pretty short of $100 million.
Today we learn that my primitive math was pretty close to the mark. Trump would need to contribute another $44 million to make good on his $100 million claim. Indeed, this month he's only contributed $33,000. (You can apparently mark him down as another major donor who has abandoned Trump during the stretch as his poll numbers have collapsed.)
The AP notes that roughly $9 million of that money has gone back to various Trump businesses, mainly the holding company that flies his jet.
This week Republicans, including RNC Chair Reince Priebus, have been beseeching Trump to put more of his own money into the race to counter a massive Clinton advantage in TV ads in key states. Good luck with that.