A vending machine at San Francisco's airport dispenses vests.

The practical outerwear is favored among Bay Area venture-capital investors.

A representative for San Francisco International Airport told Business Insider that the vest vending machine averaged $10,000 in sales a month.

San Francisco's airport has a vending machine that dispenses vests — the unofficial uniform for venture-capital investors — and Twitter has been poking fun all week.

But a representative for the airport tells us the machine's sales figures are no joke.

The Uniqlo-branded vending machine earns $10,000 a month on average, according to Doug Yakel, a public information officer for San Francisco International Airport.

At nearly $50 a pop, that means the vending machine sells about 200 vests a month.

It's one of the highest-earning vending machines that its leasing tenant — a third-party company that also sells electronics and other consumer goods out of vending machines — operates at the airport, according to Yakel. It's unclear what cut SFO and Uniqlo take.

"This is the first time we've had clothing available for sale from a vending machine, which we thought was very unique," Yakel told Business Insider.

The Japanese retailer Uniqlo started selling clothes out of vending machines in airports and malls across the US last year. At the time, these Uniqlo To Go machines stocked two of the most popular items from the brand's LifeWear collection: a thermal heat-tech T-shirt ($14.90) and a lightweight down jacket ($69.90) in an array of colors.

It appears Uniqlo added down vests for the tech set at San Francisco's airport. The men's ultra-light down vest typically retails for $49.90 online and in the vending machine.

"SFO has a down vest vending machine for visiting VCs," said Frank Barbieri, a serial entrepreneur, in a now-viral tweet that included a photo of the vending machine.

Venture capitalists can be seen sporting the practical outerwear wherever techies gather, from Blue Bottle Coffee shops to the Battery to the VC offices on Sand Hill Road..

San Francisco has chilly summers, with temperatures hovering between the mid-50s and high 60s. As investors travel across the Bay Area, meeting with entrepreneurs, sitting in on board meetings, and negotiating deals in eternal-spring weather, it helps to zip up.

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