As the USPS continues to struggle to survive they are making frequent changes in their postal rates. I have difficulty reading their rate tables that are available on line. Here is a chart produced by postal scale maker DYMO that I think does a good job of summarizing them and is current through the package rate reductions! that occurred on September 7.

I don't think PayPal has incorporated all of the reductions yet, at least in the 1st class flat rate that I use to ship chips in a padded envelope.

If you have Adobe reader, you can go to the link below and print a more readable copy of the chart that I show above.

http://s7d9.scene7.com/is/content/DYMO/Download/September_2014_Rate_Chart.pdf