"You would not expect to get a striker with his record for the price that we have paid and hopefully that will look good business if he keeps going as the way he has been," Moyes told evertonfc.com.
"In today's market, it is a massive price for some other people but we have never really been big spenders but what we have tried to do is improve the squad whenever the right players have become available.
"We might have relied a bit too much on AJ and Tim Cahill at different times and we hope he can take some of the pressure off them."
The fact that Yakubu is a proven Premier League performer was key to Moyes.
"Most people know a lot about him already but we are delighted to have him," he continued. "He has done extremely well for someone so young in the Premier League and, given his age, we hope that improves again during his time with us.
"He will give us strength and pace up front and other options.
"We want to be playing a lot of games this season and AJ and Yakubu will have their parts to play for us. But we have other people who can play up front as well."