Earlier quoted context omitted.
I'd be willing to wager that half the clocks might be wrong. It's something manager-on-duty can control, so Murphy's Law kicks in.
A standalone GPS NTP server is $750 retail. Commercial soft serve ice cream machines are at least $4000. Just building the machines with an autonomous GPS clock that doesn't need to be set, would double the revenue but only increase the upfront cost by 18%.
Moreover the $750 you reference must be a commercial product since you can do GPS on a Raspberry Pi for < $50 easily? Which product are you thinking works for this scenario? Think I've seen everything from $300 to $13000 solutions for this over the years.