Humphries, who beat Cross in the final of last week's Czech Darts Open, once again downed the former world champion with a dramatic 8-7 victory.
As well as claiming another piece of silverware, Humphries also bagged £25,000 as he continues to impress on the continental tour.
Cross, who was looking to avenge his defeat in Prague, took his opponent to a deciding leg, but ultimately fell short as Cool Hand Luke claimed his fourth tournament win of 2022.
"It's fantastic," said Humphries. "Rob's one of the nicest guys in the PDC and it's no coincidence [that] we have practiced together for the last two European Tours and made the final together.
"It was a great game, full of everything. At the start of that game we must have been averaging 113-114, it felt amazing. I know I dropped off a little bit but then I missed because Rob put me under pressure.
"I thought I played fantastic there but Rob was the better player overall because he was consistent throughout the whole game.
"I missed a couple of match darts but that 108 was clinical and one of the best out-shots of my career.
"I'm making huge strides in the game and there's a lot more to come."
Humphries improved with every game as he powered through the field. His third-round 6-3 victory over Joe Murnan was followed by a 6-0 whitewash of Brendan 'The History Maker' Dolan.
The 27-year-old averaged 100 during his win over the Northern Irish man, but he stepped up even further in the semi-final and posted figures of 108 as he beat Peter Wright 7-4.
Cross was similarly impressive on his way to the final, producing a 170 finish against Krzysztof Ratajski before averaging 110 in his semi-final win over Damon Heta.
The 31-year-old, who lost his seventh European Tour final since turning pro in 2017, said: "I'm glad I don't struggle with 'majors' to win them - these are ten times harder!"
"Credit to Luke, I thought he played great, he was the better player and if he hit doubles earlier I was out of there earlier.
"He's superb and I've got a lot of time for him."