Let's say you've got Event Staff that are booked for 55.00 per hour for a minimum of 8 hours.
If they are booked for longer, their rate increases 1.5x for each additional hour.

First, create the service in your inventory and ensure the pricing is set to hourly.

Then, we'll need to add in the minimum time booked (8 hours) and the total cost for that time (55x8=440)
Next, add in the higher rate for the additional hours. 55.00x1.5 = 82.5. For an additional 8 hours that would come to 660.00

Finally, on a project, if we add the item for 9 hours, we'll see the rate correctly calculate to 522.50