Lehman's first individual Champions Tour triumph - he teamed with Bernhard Langer to win the 2009 Liberty Mutual Legends of Golf - was worth $360 000.
After Lehman began the sudden death playoff on No 18 with a tee shot down the fairway, Couples's only bad tee shot of the tournament veered left into the shrubs, forcing him to take a drop.
Frost's tee shot ended up in the left bunker and he pulled his second shot left of the gallery. He cleared out dozens of pine cones in between the ball and the green before playing his third, which was nestled in a shrub, across the green.
Frost and Couples finished with double-bogey sixes before Lehman's birdie putt from 12 feet came up a fraction short. He smiled, tapped in, pumped his right fist and cradled the silver trophy.
Since turning the requisite 50 years old in October, Couples has energised the Champions Tour, winning half of the six events he entered before coming to Colorado, where the thin air favoured his long drives - but not in sudden death.
After congratulating Lehman, Couples put his head down and stormed toward the clubhouse, where he quickly grabbed a couple of irons out of his locker and bolted for the parking lot.
"It's pretty disappointing," was all Couples had to say as he hustled to a waiting car.
After back-to-back eagles on holes 15 and 16, Couples had a chance to win this tournament outright in regulation but his eight-foot putt for birdie on 18 missed by an inch.
His tap-in left him with a 69 and in a share of the lead with Frost (67) - who had trailed by 12 shots coming into the weekend - and Tom Lehman (71).
Lehman began the day as the co-leader with Jay Don Blake, whose eagle on No 7 gave him a two-shot lead that lasted but a few precious minutes.
Blake, whose winless streak was extended to 396 starts, sauntered onto the eighth hole before topping his tee shot 30 yards into the bushes.
"I just totally shanked one, shanked it right into a ditch," Blake said. "From then on, I felt like I couldn't really be at ease at hitting some good iron shots. I was pretty cautious all day. That kind of put me in a bad frame of mind."
Mark O'Meara (71) finished two shots behind the trio in the playoff and Nick Price (70) finished three strokes off the pace.