However, this estimated cost may in some cases differ from the final cost of the order. For example, it may happen if the pro indicates that the task took longer than estimated upon completing it, since the final amount is always calculated in accordance to actual time spent doing the job. This is why we advise you to always contact your pro before they arrive on site, and ask how much time they believe the task could take. It's also a good idea to clarify whether they will need to make any additional purchases for your task, as these expenses may also alter the final cost of your service.