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Mark Zuckerberg has more money than one could ever possibly spend, but he's still pinching pennies ... and his hunt for a bargain brought him to Costco.

Check out this pic of the Facebook founder and CEO in the TV aisle of the budget store in Mountain View, CA ... it's not exactly the place you'd expect to find a multi-billionaire. He seems to be in the market for a monitor.

Seems Zuck's just like the 99 percent -- aside from his estimated net worth of $77.7 BILLION -- looking for a deal during a holiday shopping spree.

Most members of the three comma club would send an assistant to handle such pedestrian tasks, but not Mark ... instead, he's rolling up his sleeves and braving the outside world with his wife, Priscilla Chan.