I mail a lot of things that I sell. Shipping is usually no problem because the transaction goes through my Etsy site and I’m able to access the least expensive shipping options thru the site.
What really ticks me off is that if I sell one of my pieces to a person outside of my site, then I have to go wait in line at the post office because they don’t give me the most cost effective options through the USPS site. This doesn’t make sense! The government has been yelling about being green for years now. But, instead of making it easier to use USPS, they make it harder and require me to use gas driving to a branch office instead of doing it online.
Buying the postage online saves gas, cost for the post office itself thru staff, and prevents long lines. If the post office wants to compete with FedEx and UPS, then start thinking outside the government box. Make it easier to use you and then people will do so. As it stands, if one of the other shippers provided inexpensive shipping options then I’d probably never use the post office again.