Depends on the item - if it's still in common use, for example.
Making obsolete kit, especially if electronics get involved, is actually probably harder than contemporary kit.
Imagine you want to have a Comptometer built* today. This is a TL5 computer in a TL7 society. There will be no existing models from a supplier, and if you find someone who'll custom-assemble one (Dell-fashion), they will in turn have to find someone who'll custom-fabricate the components, because there's no mass supplier of
them, either.
Not only do items go obsolete, but entire skillsets get lost as you move up through the TLs - Stonemasonry is an obvious one, but some important metallurgy skills were lost in the industrial revolution; that's why we've only got our best guess these days as to how Toledo/Damascus/Wootz steel was made.
A discount is only going to occur if something about the new abilities you have at a higher TL makes it genuinely easier to mine/machine/assemble/whatever. I can imagine, for example, bulk fabrication of stuff in bonded superdense becomes easier at higher TLs because you finally get industrial tools that can actually cut the bloody stuff; if it can resist a nuke then an oxy-acetalyne torch is not going to do the job....
* If you're not old enough to remember what that is without looking it up, see here:
http://en.wikipedia.org/wiki/Comptometer
. If you are old enough to remember what that is without looking it up, you are very, very old.
