A sales seat is an administrator or a salesperson, somebody who can change what the business sells and owes. A production seat is the shop floor, which reads the work and records what it has done. Seats of each kind get cheaper from the fourth.
Prices are in Canadian dollars. A US dollar price is not available yet, so your card is charged in Canadian dollars and your bank converts.
A card is taken at signup and nothing is charged for 30 days. You can add or remove seats, or switch between monthly and yearly, under Settings at any time.