How do you make money out of math? By seeing patterns in numbers that nobody else can. We just spoke about how actuaries will notice data correlations which suggest a link between events that nobody else has recognized; a mathematician can do that for any industry and any purpose. It's almost like they're reading the base-code of the universe in one of the 'Matrix' movies.
Math has a number of purposes in modern living, from exploring theories to addressing practical problems. How much force is needed to move an oil rig? How strong must the foundations of a building be to support what has to go on top of it? How much fuel needs to be in a spacecraft? If you don't know, you better contact a mathematician to work it out for you. They're great with big numbers, as you'll see when they present you with their invoice.