The siblings reached out to fans for prayers for their older brother Tom after he underwent quintuple bypass surgery on July 7, but the dollar-conscious duo continued to tour while he was at death's door.
While Tom, 70, went under the knife in Utah, the former teen idols were far away, performing at the Horseshoe Casino in Bossier City, La.
"Donny and Marie said they didn't want to disappoint their fans, but I believe they didn't want to miss a paycheck," a source told Radar.
The pair averages a whopping $53,494 per show, according to music industry bible PollStar.
As Tom recuperated, Donny, 60, and Marie, 58, performed at the Hard Rock Hotel & Casino in Tulsa, Okla., on July 8, and Ryman Auditorium in Nashville two days later.
Despite the snub, Marie posted a seemingly heartfelt note about Tom, saying, "My greatest wish for him is to enjoy a second chance at life and have many more years on this earth."
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