Amazon initially aimed to release the product this year, but the timing was pushed out after the team encountered technical issues with the device, one of the people said. It was a costly endeavor and required significant upfront investments for lab research and development, in addition to the high salaries for scientists and engineers, the sources said, adding that the team's weekly overhead was roughly $1.5 million. Amazon didn't comment on the figure.

Only one project now remains active within Grand Challenge. Its focus is on health tech, the people said.