I got a rate of $2.54 from ebay for shipping 3 ounces via USPS thick package, 1st class. The rate quoted for 4 ounces was $2.60. My guess is they have the wrong rate table loaded as the 2016 USPS rate should be the same for 3 or 4 ounces (or even 8 ounces). We'll see if the printed label for the lower rate gets accepted by the postal service or returned for more postage. 
If you want to see ALL the 2016 postage rates, you need Notice 123 from the USPS. There are dozens of categories now, so no surprise that two formerly related companies come up with different customer prices for commercial mail. See the link below:
