7/16 shields can't drop any more. So as Surge says, they are insanely rare. There is a set of three 7/16 celestial shields with pvp mods out there somewhere, but at least 1500e each, probably more if you can find them. I sold that set a year or so ago for 3000e.
8/16 and 7/15 still drop, so aren't so expensive, with the notable exception of Darkwing defenders and Enamelled shields. There is a couple of 7/15 darkwings on Kushy's thread I think, but he's asking an insane 200a each.
Apart from that, expect to pay:
15-25e for 7/15 and 8/16 common blue skins, more for the rarer skins.
45-75e for gold versions of the same common skins.
More for rarer skins of course.
On another note, I recently sold a 7/16 shield with -2/Ench -2/stance (dual reduction)for 1500e to a player saying he wanted it for pvp. I don't know if those are pvp mods, but that's what he claimed.
I may be prepared to sell some more like this one from my collection, but you'll have to impress me 
Hope that adds something to the discussion....
Max
