I've heard this argument before and it's predicated on a set of assumptions about savings rate that may not hold true.

It's easy to come up with a plausible set of numbers where the absolute savings are better in Austin even allowing for it being a greater percentage of income.

Beyond that though, I would submit two other caveats:

1. If you were to become involuntarily unemployed in San Francisco for any length of time then you will find your burn rate is still the SF burn rate and not the Austin burn rate.

2. Spending your twenties in a Gold Rush town with the intent to move to some other more rooted town later means you don't put any roots (professional or otherwise) down in that other town. You may find yourself with no connections and no relevant experience when it's time to move back to Grand Rapids.