How many people attended Super Bowl LVIII in person?

How to get close to this number

Stadium capacity is the whole answer. An American football stadium holds somewhere between sixty and eighty thousand, and the final is played at one venue like any other game. The attendance cannot exceed what the building holds, which is a much tighter constraint than the event's cultural footprint suggests.

The ratio in the explanation is the point of the question: roughly one person in the building for every two thousand watching on television. The event is one of the largest broadcast audiences on Earth and one of the more ordinary stadium crowds, and the gap between those two facts is what makes the physical attendance figure surprising.

The allocation explains the resale prices. A large share of seats goes to sponsors, the league and the two participating teams before any go on general sale, so the number available to ordinary buyers is a fraction of an already limited capacity. Scarcity here is manufactured by distribution rules rather than by the size of the building alone.