"The [large, double-edged knife] cost me a whole stack of gold coins. It was a little less than a cubit in length, almost a short sword, and the mounting of the blade was covered with a strip of silver, so if you wished you could even risk a fight with someone who had risen from the dead."
- Shadow Prowler, Alexei Pehov
So it's probably a fine long knife ("almost a cubit" means probably a bit under 18"), possible balanced, definitely silvered. Could run as much as $1200 (+9 CF for all three), which is a reasonable stack of gold based on the prices we see in the books. It's not crazy, anyway.
One thing that made me want to write it up - the effect of silver on the risen dead. The undead - zombies, especially - are scary as all get-out in these books. They're not cannon fodder, to be chopped to bits by any given fighter or turned by a priest. They're flesh-eating creatures with a dangerous bite, extremely hard to kill, and while vulnerable to silver it's not really enough:
"I could quite easily be lucky enough to walk away from such a skirmish, even if my arm had been torn off."
I like a universal vulnerability. It gives PCs a good handle on what to use. My own DF game doesn't feature this enough, so people tend to guess. That's fine, too, but it's empowering to the players and world-building if you have specific effects. If the undead are always scary . . . and silver is always useful (or potentially so) against them, you have already learned a lot about the world and how to interact with it. That's never a bad thing.