Was there a standard rate they were paid at? i.e. were the soldiers of the group paid their normal army wages? Or was there an amount (or bonus) specifically for the expedition?
It would be great for a Jefferson expert to weigh in. But to get things started, here is a transcription of President Jefferson's clandestine letter to Congress requesting $2,500 to fund the expedition. I do know that on February 28, 1803 Congress approved this budget. But how it was divvied up I couldn't tell you. The Monticello Foundation is a great place to start for the original documents, including things like packing list for the expedition, who and where Lewis studied with, and correspondence between L&C and Jefferson. But the specifics of your questions are a great ask.; I hope we can hear more.