Be sure to see the update below.
Although there have been a multitude of shipping problems and confusions with eBay's implementation of the last postal rate change, I have not seen this one discussed anywhere, except for a seller's board that I'm on.
In short this affects every seller who uses Calculated Shipping on eBay and the new First Class weight amounts of 14-16oz.
eBay is charging the buyer incorrectly for these amount, but is charging the seller correctly when they go to print the label. I think this is particularly insidious because not many sellers check their postage costs on a listing. It's also particularly bad if the seller had an additional handling charge.
Via calculated shipping, the buyer is being shown the rate of $6.45 for 14-16oz FC postage, plus of course, any handling charge they have. When the label is printed, the seller is only being charged $3.60 (TRS) for this same label.
This is particularly egregious if the seller has a nominal handling charge, as it is making with a $1.95 handling charge, a local sale of a 14 oz item = $8.40, an inflated amount. By contrast, the seller is only being charged $5.55, a still reasonable cost.
This is no doubt happening because there is no USPS retail rate of 14-16oz First Class. Therefore it is my guess that eBay's calculated shipping, has no idea what to put into those fields as a base, so it defaults to the Priority Mail rate for 14-16oz, as that's the only thing available from USPS if you were to walk into a post office. When it should actually be defaulting to a small increase over the 13oz FC rate.
I have taken my handling charge off of a 14oz FC item, so you can see for yourself. This is a known problem amongst some sellers, but I have not seen anything to indicate that eBay knows about it. There are several workarounds, none particularly good.
I hope you can get some answers from eBay in regards to this!
PS: I rounded it the oz in my note to say 14-16oz rather than get into the whole 15.999 thing, as that has nothing to do with this problem.
Note from the Editor: This is similar to a problem we covered in January, but not specifically for Calculated Shipping. We sent an inquiry to eBay on Saturday to see if either problem has been resolved.
Update 2/21/16: eBay responded to our inquiry about shipping rates raised in this letter to the editor:
As for the second piece, 14-15.99oz first class package at commercial pricing is only offered through online printing tools like eBay labels, and is not available at retail locations of the USPS for purchase. We allow sellers to specify in their shipping preferences if they want to charge retail or online/discounted rates.
If a seller specifies retail rates in their preferences, then we display a price which is available for Priority Mail at retail in the 14-15.99 weight range (6.45) to help seller cover their retail shipping cost at the USPS store. If the seller sets their shipping preference to charge online/discounted USPS pricing, the buyer will be charged the same rate as Ebay labels charges for 14-15.99 (3.55-3.65). Detailed chart is also show in the same AB post above.