One of the reasons shipping has gone up recently on eBay is that back on May 17th of this year...the Post Office instituted MAJOR changes in their tariff. This is something many of you may not be aware of.
First Class doesn't even exist anymore over 13 ounces! It's now gotta go Priority Mail if it's more than 13 oz (unless you want slooow Parcel Post with no Delivery Confirmation)
Also there are now 3 different rate categories within First Class with new strict restrictions regarding size: Letter, Large Letter, and Parcel. Based on size AND thickness. And it can even get bumped up a category if your packing makes it unbendable!
BUT...if an envelope is too thin...it doesn't qualify for First Class parcel and the 18 cents Delivery Confirmation option goes up to something like 65 cents and they have to manually fill it out rather than online label printing.
A small item protected with cardboard now likely falls into the "Parcel" rate category in First Class. By the time a shipper pays for an envelope, cuts some cardboard for protection and gets it ready to ship...it's not uncommon to be in the $3 to $3.50 range even if super light due to packaging costs and the new much higher First Class Parcel rates! Might as well toss the extra buck in there and have it go Priority in a nice Post Office supplied box!
That same small item in an envelope protected by cardboard...used to be able to go out AT LEAST a dollar less.
Got a family member who ships a lot. They've really been complaining about these new Postage rates and rules. And her customers are too...blaming her and then she has to send elaborate explanations as to why she didn't offer First Class as an option.
Her international customers are REALLY complaining. Many items past a much lower ceiling weight can't be shipped International First Class at all now...the more expensive International Priority Mail is the lowest cost option now.
She also said even her regulars at the Post Office are pulling their hairs out over the new rules...they are so complex now. They have to fit every envelope through a slot to make sure it fits the rules, etc, etc.
AND...she mentioned there were some MORE new rules regarding 13 ounce First Class that were to go into effect just a couple of days ago on July 31st. But I don't recall what that was all about.
Anyway...I think all of the above is why a lot of eBay sellers are probably going Priority Mail only. Probably a lot of time it's only a buck more and they don't have to buy an envelope or box and cut cardboard and all that. Just drop it in a Post Office supplied Priority Mail box and off it goes...with the 65 cent Delivery Confirmation free too (if label is done on the web). That saves both sides 65 cents.
She hates it cause it pushes her net prices up now...and that deters many customers. But it's clearly the Post Office that has now tweaked their tariffs to force all those old First Class Mail shipments into their Priority Mail product.