Yeah, the New York Times article at [1] lists the things that go into that number, including: $578 on extra clothes and shoes, $235 on entering other races as practice, a $130 gym membership, and $210 of sports massages.

This wasn't someone trying to keep their costs to an absolute minimum.

[1] https://well.blogs.nytimes.com/2016/07/15/the-1600-marathon/