Smith averaged 103.89 in the final and landed 11 maximums, form that made him the sixth different winner of the event since it began in 2015.
It was also his first major since the 2022 European Championship, a four-year gap closed with one of the cleaner finishing displays of his run so far.
The final was closer than the scoreline suggests. Smith scored heavily from the start, but Price kept pace and levelled at 5-5 courtesy of an 11-darter, although that was as good as it got for the Welshman.
Smith answered with back-to-back checkouts of 123 and 127, and those two visits triggered six legs on the spin. He went from 5-5 to 11-5, sealing the win with a 14-dart break of throw.
"I'm absolutely made up with the win, I'm just so happy," Smith told the PDC afterwards.
"You're playing Gerwyn Price, he's one of the best players in the world. You've got to up your game, so to beat this man, wow.
"Since the World Series, on the Euro Tour, everything has clicked. Sometimes you need a kick up the backside, and maybe that's what's done it."
His route to the title carried the same weight of scoring.
Smith saw off Kevin Doets and Daryl Gurney to reach the closing day, then beat Josh Rock 10-7 in the quarter-finals before ending home favourite Gian van Veen's tournament 11-8 in the last four.
Seven 180s and two ton-plus finishes carried him through that semi-final, and into only the second major final of a career he has won both times he has reached one.
Price was chasing a third World Series Finals crown, having won the event in 2020 and 2022, and for three days he looked capable of it.
The Iceman barely missed a double against Brody Klinge on Friday, dispatched Canada's Jim Long with little fuss, then produced a 103.86 average and a 170 finish to beat James Wade, closing that match with four legs in a row.
An 11-7 win over close friend Jonny Clayton, wrapped up at an average north of 104, booked his place in the final.
'I was rubbish'
"I was absolutely rubbish in that final, but don't take anything away from Ross, he was brilliant," Price said.
"He took his opportunities and some big checkouts at the right time. But I'm very disappointed.
"I'm playing some good darts and earning some good money. I'm absolutely gutted today, but I'm doing well - I think I'll be fine!"
The day's other headline belonged to the man Smith beat in the semis and the man Price beat in his.
Clayton was responsible for the tournament's biggest shock earlier on Sunday, thrashing Luke Littler 10-4 in the quarter-finals to end the teenager's bid for a clean sweep of 2026's World Series events.
The defeat was Littler's first at a Premier event in 330 days, and it arrived on an afternoon when the 19-year-old could not find his range. Van Veen, meanwhile, edged Dutch compatriot Dirk van Duijvenbode 10-8 in the last eight, reeling off four straight legs including a 12-dart hold and a 124 finish on the bullseye.
For Smith, none of the noise around Littler or the near misses from Price much matters. He arrived in Amsterdam in the best run of his life and left it a two-time major champion.
Finals Day results
Quarter-finals:
Ross Smith 10-7 Josh Rock
Gian van Veen 10-8 Dirk van Duijvenbode
Gerwyn Price 10-7 James Wade
Jonny Clayton 10-4 Luke Littler
Semi-finals:
Ross Smith 11-8 Gian van Veen
Gerwyn Price 11-7 Jonny Clayton
Final:
Ross Smith 11-5 Gerwyn Price