If you want to check your expenses, click on 'Event overview', then navigate to 'Reporting and Expenses' tab.
You can have an overview of different expense types, like:
* the flights booked
* the average cost per flight
(see the example below)
You can also compare costs from different events or you can compare accommodation and transportation. Thus, you can clearly see that your first event cost you more for accommodation than for transportation, for instance.