Where I live, I have to calculate (and show the process of calculation) the cheapest cost of getting to and back from work from my house. My boss simply pays me that much each workday. If I move, I have to do this calculation again. It doesn't matter how long it takes me to get to work (i.e. I'm not "on the clock"), they are simply imbursing me for that part.

Ironically, sometimes moving further away is both cheaper and faster.