You have to consider the trajectory. SF is already a dumpster fire, if enough affluent people leave, property prices will tank and you will be paying off a mortgage for a larger sum than what the property is worth.

Meanwhile, all these affluent people have to move somewhere, the properties in these places aren't going to stay cheap forever. So you can get a cheaper mortgage in those places to pay off a property that will rise in value.

Of course, that's all speculation. Prices in the "good places" are already high anyway, if you really want to strike a bargain you have to buy into the places that are still up-and-coming.