Thomas, Bednarek hit jackpot at Grand Slam Track meet
Thomas, who had stormed to a convincing victory in her specialist event the 200m on Friday at Kingston's National Stadium, took second in 49.14sec behind Bahrain's Salwa Eid Naser, the 2019 world champion who finished in 48.67sec.
Marileidy Paulino of the Dominican Republic -- the reigning Olympic 400m champion -- was third in 49.35sec.
"I'm not sure I've ever been more tired in my life," Thomas said afterwards. "I knew that was going to be one of the hardest races of my life just because of the talent in the field."
Thomas's combined results over the two races made her one of the four athletes racing on Saturday to win $100,000 each for their performances over the first two days.
"I heard them saying on the home stretch '$100K on the line' and it really, really motivated me," the 28-year-old said following her race.
Other athletes to hit the jackpot on Saturday included two-time Olympic 200m silver medallist Kenny Bednarek, who completed a short sprint double with victory in the 200m after winning the 100m on Friday.
US sprinter Bednarek cruised to a convincing victory in the 200m, storming home in 20.07sec.
Britain's Zharnel Hughes took second in 20.37sec while 2022 100m world champion Fred Kerley of the US was third in 20.39sec.
"I got to pick up the ultimate prize," Bednarek said after his win. "Everybody's getting paid and that's what we need in this work, no matter what the competition."
British 400m star Matt Hudson-Smith meanwhile collected the $100,000 prize in the men's long sprints category with a victory in the 200m in 20.77sec, a day after finishing second in the 400m.
"It's great to win the first Grand Slam championship, especially in Jamaica, the home of sprinting," the 30-year-old world and Olympic 400m silver medallist said.
Hudson-Smith said he had no plans to splurge with his hard-earned payday.
"I'm just going to save it," he said. "I'm coming to the end of my career, I've made a lot of big purchases -- and now it's time to start saving."
The other $100,000 winner on Saturday came in the women's short distance group, where Ethiopia's Diribe Welteji backed up her second-placed finish in the 800m on Friday with a victory in the 1,500m in 4min 04.51sec.
In one of the most competitive races of Saturday's second day, Kenya's Emmanuel Wanyonyi, the 2024 Olympics 800m gold medallist, upset a high-caliber field in the 1,500m.
Wanyonyi won in 3min 35.18sec, leaving US runner Yared Nuguse in second with Olympic 1,500m champion Cole Hocker third.
Britain's Josh Kerr, the reigning 1,500m world champion finished fifth.
In the women's 100m hurdles, Tia Jones of the United States won in a world-leading 12.63sec, with Jamaica's Danielle Williams second in 12.70sec and Puerto Rico's 2020 Olympics champion Jasmine Camacho-Quinn third in 12.70sec.