Gratify calculates an hourly rate at the time of task creation depending on supply/demand of Gratify freelancers. A freelancer bids on a task by reporting how many hours they think the task will take. Hourly rate * hour estimate curates the initial task bid, which is then subject to counteroffers between freelancer and client.
Pricing is always per-task. You will only be charged the amount you and the freelancer agreed to (plus a transaction fee of $2) after the task is complete.