The above environment is from the Nicholaz viewer but I tested it in the normal releases available as well and the issue persists there too. Given that this wasn't happening a few weeks ago and is happening to many of us now without a viewer upgrade I doubt this is related to the viewer at all.
Issue is as follows:
Sets of unlinked prims taken into inventory as a group that have some items set to sale for different prices no longer retain those individual prices and now default to the same price across. It seems to be the price of the last for sale item selected. This was not happening as of two weeks ago.
For example I have two store locations with the same building on them. I set things up on one parcel and then take-copy to inventory and place it on the new parcel. Previously the vendor boxes would retain their varied prices, now they default.
Attached are two screenshots; the file "primold" is a set of vendor boxes that have been out for two weeks. You can see the selected box is set for sale at L$200 (which matches the graphic on the box as well)
"Primnew" is the same set selected and copied from the above with the new issue. The same prim is now set for sale to L$150.