When you book a task, you choose a Tasker based on their skills, reviews and hourly rate. The hourly rate you see is inclusive of the payment for your Tasker and the 30% TaskRabbit service fee. Your Tasker sees the price that you pay, as well as the exact hourly rate they will earn.
For example, if you pay $100, $70 goes to your Tasker. The TaskRabbit service fee is 30% of the total price you pay for the task, excluding any reimbursements made to the Tasker (they get 100% of any reimbursements).
A 7.5% Trust & Safety is also added to the total of the task. More information on this fee can be found here.