The Irishman told the Birmingham Mail why the in-form former Watford player is to be put on a par with the club's highest earners.
Young still has three years left on his current deal following his £9.5 million move from Vicarage Road 19 months ago.
"He has some quite considerable time left on the contract but he's been brilliant", said O'Neill.
"When we signed him from Watford we paid a lot of money 'for' him but we didn't pay a lot of money 'to' him and that's fine.
"He was a young kid and he was happy to do it.
"It was still a lot of money to pay for him, but at the end of the day he might be worth three times that now. It's all relevant now.
He was voted in the PFA team and that's a big compliment. The progress he has made in the time that he has been here is astounding."