Price, who was playing in a fourth Grand Prix final, claimed the first set with a stunning 132 three-dart average.
He raced into a 3-0 lead and Humphries admitted afterwards that avoiding a 6-0 clean sweep was on his mind such was the brutality that Price was producing.
The fourth set saw the momentum swing however. With Price waiting on tops to move to within two sets of victory, Humphries nicked it by taking out a brilliant 105, with what he said “felt like the biggest shot of my career”.
From there his levels started to rise and he claimed the following three sets to lead.
Price rallied in set eight and won three successive legs to force a best-of-three finale, but, after a short break, Humphries found another gear.
Set nine went to a deciding leg, but unlike the previous four sets in the match where that had happened, there was a break of throw, with Humphries finishing in 10 darts.
That left Price dejected and Humphries won three unanswered legs to claim a ninth major PDC title.
“The sport is in such a special place that when you pick these trophies up they mean a lot more,” said Humphries.
“When I was winning, I don’t think there were so many good players. I’m happy to win a couple a year – one a year is great.
“To go on and win like I did is going to be tough. I don’t think I can’t do it, I’m just trying to pick up as many titles as I can.
“I worked incredibly hard, showed a lot of grit and determination. I think these are a lot sweeter than the ones you win with ease.”