Business interests just dropped another $2 million to fight a labor union-backed ballot measure that would ratchet up San Francisco's so-called Overpaid Executive Tax. That brings the war chest against this proposal to serious money — and it tells you everything about how high the stakes are.

For the uninitiated: San Francisco already taxes companies based on the gap between executive and median worker pay. The new measure wants to crank that up further. Proponents frame it as accountability. Opponents call it yet another reason for companies to leave a city that's already bleeding talent and revenue.

Here's the uncomfortable math. San Francisco's taxable income base has been shrinking. High earners are relocating. Remote work made it painless to decamp to Austin, Miami, or even Sacramento. And yet — as one local pointed out — "SF's budget continued to rise to all-time highs." Let that sink in: fewer taxpayers, more spending. That's not a formula for sustainability. That's a formula for a fiscal cliff.

Now, reasonable people can disagree about whether CEO-to-worker pay gaps are obscene. Many are! But the question isn't whether we find something distasteful — it's whether piling on another tax in a city already notorious for driving away businesses actually helps workers. If your employer relocates to a friendlier jurisdiction, your pay gap problem is solved in the worst possible way: you don't have a job.

The $2 million campaign spend is eye-popping, sure. But it reflects a rational calculation by businesses that this measure could cost them far more. And they're not wrong to worry. San Francisco has a well-documented habit of treating the private sector like an ATM — then acting shocked when the ATM gets up and walks to another state.

As one SF resident put it plainly: "Can't blame them, everything is expensive here from owning a property to paying taxes."

The real question voters should be asking isn't whether executives make too much. It's whether San Francisco can afford to keep testing how much punishment its tax base will absorb before there's nobody left to tax. The answer, increasingly, is no.