The 28-year-old has been a star on the European Tour over the last 18 months, winning five titles, but has now transferred that to the PDC Tour.
He proved he belongs on the biggest stage after producing the performance of his life in Leicester, taking down the 2020 champion Price 5-2.
The foundations of the win were laid when he claimed 10 out of 12 legs, including a stunning 170 checkout, to move 3-1 clear and then he sealed his title with a sumptuous 138 finish.
Victory moves him up to fourth in the world and is the biggest title of a blossoming career, with a £120,000 payday.
Former world champion Price was the heavy favourite for a second Grand Prix crown, but could not keep up with Humphries’ heavy scoring.
And the triumph allows Humphries to give his son a special present on his first birthday on Monday.
“It is one of those feelings you can’t put into words,” he said. “I have imagined this moment all my career and to actually finally do what I have always dreamed of, you can’t put it into words.
“There are no superlatives to say, it’s unbelievable.
“Taking out 138 out under the most pressure that I have ever been under, just made the whole thing a lot better, there was no better way for me to win. I am so proud of myself.
“It’s my son’s birthday tomorrow, as much as he won’t know it his life has changed because his dad is a major champion now and that is quite massive.
“I would have loved to have him here, but he’s going to have a very good present, I’ll have to wrap the trophy up so he can see how great dad is.”
Price had to endure the usual hostility from the crowd, who were pro-Humphries in their support and will now be hit in the pocket after swearing during his on-stage interview.
“It’s one of those games, I am absolutely gutted but it’s what happens,” he said.
“I wish we could play these games in Wales, it’s frustrating sometimes. I didn’t help myself early on, Luke played fantastic, he’s a worthy winner. But I think I played better overall.
“He had a lot of support. I’ve got a good man cave to go back to, I don’t give a s**t.”