The Concorde mainly transported fuel across the Atlantic so that enough was available to land safely. Passengers were just an extra on top. Also, being first-class only, it held fewer passengers than what low budget airlines have taken to cramming into their planes lately.
To look at the structure relative to passengers is a bit misleading. Let's look at the fuel load and the mass fraction of empty weight relative to MTOW instead:
| 747-100 | Concorde | |
|---|---|---|
| MTOW | 333.4 tons | 186.88 tons |
| Empty | 162.5 tons | 78.9 tons |
| Fuel | 183,380 liters | 119,800 liters |
| Fuel/empty mass | 1.1285 L/kg | 1.5146 L/kg |
| Mass fraction to MTOW | 48.74% | 42.22% |
If you compare passengers plus fuel to the empty mass of each airplane, the Concorde actually comes out well ahead of the 747 and looks like a prize of lightweight design. Having structurally efficient delta wings helped and should explain most of the difference.
