You guard your money and spend your hours like they're free. But time is the one account that only ever withdraws, never the cheapest.

The thought behind it

This line works by turning the expected explanation inside out: the thing you were blaming turns out not to be the thing. The TIME thread runs straight through it: an account that only ever withdraws, and never quotes you a rate. Everything hinges on “cheapest”, which is the part a politer version of this sentence would have left out.