Pre-bought: 20 people * $155 = $<<20*155=3100>>3100
Gate bought: 30 people * $200 = $<<30*200=6000>>6000
$6000 - $3100 = $<<6000-3100=2900>>2900
The passengers that paid at the gate paid $2900 more dollars than those who pre-bought their tickets.
#### 2900