The price is shown on the Priority Review checkout before you pay, and that is the total: a single one-time charge. It covers the application you buy it on and every application you send in the next 30 days. There is no subscription and nothing renews.
Some roles carry their own price, so the checkout always shows the price that applies to the application in front of you.
Monthly subscriptions from the earlier billing option keep the rate they were signed up at for as long as they stay active.
Something not right with a charge?
Send a change request: billing mistakes our records prove are refunded automatically, and a person answers the rest within two business days.