"It's looking as if it's dead in the water," Williamson told the Plymouth official website.
"His club are looking for a transfer fee of a few hundred thousand pounds and that was not the information we were given when the boy came over.
"If that information was known to us, we would not have brought the boy over in the first place.
"He's out of contact in the summer. We'll keep an eye on his progress and maybe something will happen when he becomes a Bosman player.
"The situation has changed as far as we are concerned. The goalposts have certainly shifted.
"We're not prepared to pay the money that Sturm Graz are looking for."