The ones I saw were at Sprue Bros. site for $15. I was looking for ETO decals and the ones at your link appear to only be for the PTO.
As for the price, yes, they are cheaper than the current price of a Sherman, however I got mine for $10 each, so $15 is a bit steep for me as these are are "practice" models for getting back into the hobby. Made a few mistakes on them so far...but learning.
Thanks