Pardew has chased a number of players from across the continent during the close season but has been unable to conclude deals, including missing out on French international defender Mathieu Debuchy.
The Magpies boss told The Sun: "You ask any Premier League manager, outside of Chelsea, and we are all worrying about where to pitch.
"The big problem we have as football managers and chairmen is the valuation agents are putting on their players.
"They need to understand times have changed."
Newcastle kick off their Premier League campaign at home to Tottenham Hotspur on Saturday, August 18.