Maddison has been at the heart of the good vibes that have returned to Tottenham despite the sale of talisman and record scorer Harry Kane (29) to Bayern Munich.
Another classy display on Saturday helped Tottenham move to seven points from three games -- Maddison putting his side in front early on and oozing class.
One reporter asked Postecoglou whether the former Leicester man could turn out to be the 'bargain' of the summer.
"A 45 million pounds bargain! I don't know what world you live in mate?" the Australian former Celtic manager who was a surprise choice for the Tottenham job, shot back.
"But I know what you mean, relatively so. There wasn't anyone happier than me when we got him. I was delighted.
"I wouldn't say I'm surprised, but I'm overjoyed at the footballer I've got."
Tottenham finished a turgid eighth last season with Antonio Conte at the helm until he was sacked in March.
The mood was gloomy with fans desperate for a return to the style of football they believe Tottenham stand for.
After Saturday's win they were singing "we've got our Tottenham back" with Maddison already a firm favourite.
"The way he's embraced the whole club, where he's at in his life. He really wants to be the person. He's that creative force for us. He works hard, he wins the ball back, presses," Postecoglou said. "And I think there's more to come.
"When he gets more understanding with our forward players and they get more understanding with him. He's going to keep improving. If we got him in the bargain bin, that's great."
Maddison's form has rubbed off on his teammates although striker Richarlison (26) continues to struggle and it would not be a surprise if Tottenham looked to bolster their attack before the transfer window closes.
Richarlison missed two good chances, both provided by Maddison, and was eventually subbed off.
"Richy will work hard, he's a good footballer, he'll get his goals. What's more important for me is that he keeps contributing to what we do as a team because ultimately we're not going to get to where we want to on the back of one player scoring goals," Postecoglou said.
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