If a cab ride costs $2.5 per mile, and Briar has to go to an event 200 miles away, he will spend 200* $2.5 = $<<200*2.5=500>>500 one way to the trip.
Since the round trip is also 200 miles and Briar is charged $500, the total amount he spends in a day to go to the event and back is $500+$500 = $<<500+500=1000>>1000
The event is one week, meaning Briar will have to spend $1000*7 = $<<1000*7=7000>>7000 on the cab rides
#### 7000