What is cheaper priority mail or parcel post?

Rates for parcels are quite complicated. I do not think they use the term "parcel post" anymore. They do have something called standard mail which is usually cheaper and slower. However, there are flat rate boxes and envelopes which are priority mail and not dependent on weight and cheaper if your item will fit into one. There are special rates for media. There are optional extra fees for insurance and tracking. You also have to go the post office to mail anything over one pound. I suggest you go to the post office and ask for the lowest rate, if that if what you want.