Variable postage costs between search function & actual listing

Has anyone noticed that there is variable postage rates on listings. When you look at a lot of the listings under the search function the postage price is displaying as a lot less. When you click onto the actual listing the price automatically increases by 10-15%. I have seen a large number of newly listed items showing up this way. There are of course others that do not. Does anyone know if this has anything to do with the new fee structure beginning in May? If so, it makes no sense as the additional costs do not equate to 9.9% FVF.