Tiger Global just valued a bagel shop at $300 million. And the math actually makes sense if you stare at it long enough. PopUp Bagels started in 2020 out of a kitchen in Westport, Connecticut. Adam Goldberg was baking bagels for neighbors during the pandemic. Five years later, Tiger Global closed a deal in late March that values the company at 5x what it was worth five months ago. The unit economics are what caught Tiger's attention. Average transaction over $24. Five bagel varieties. Three…