8 oz. package sent FC = $2.56 postage +.10 envelope (poly mailer bought on Ebay) + .19 DC from postage online =$2.85 and I leave it in the mailbox for carrier to pick up.
Same item sent in the "free" PO tyvek envelope would be $4.80 to $5.83 (paid online).
I don't use PM unless it is over 13 ounces or it has been requested and paid for.