Starbucks likes profit. I can't blame them. A worker can prepare a customer order in 90 seconds. Longer than that, and they will leave the store. Customers walk into Starbucks at an average rate of one every 120 seconds.
Customers arrive non-uniformly.
The rest of the hour will see 25 more customers at 2.5 minute intervals. Given this scenario, Alice will have the minimum wait of 90 seconds. Similarly, Janet will wait 225 seconds and I will wait 165 seconds. By the time Michael comes in, Suzanne has finished all the preceding orders, so he only waits 90 seconds. This will also be true for the rest of the customers that hour.