Why does Moonves think Star Trek has to make more money than
"The Big Bang Theory" & "CSI: [Insert Some City Here]" for him to consider it?
Isn't "as much money as ...." or "a lot of money" valid enough reasons?
It's called opportunity cost. There are a limited number of hours that CBS has to show new programming. To maximize revenue, Moonves wants to fill those hours with the shows that will make the most money. If giving Star Trek an hour a week means canceling CSI: XYZ, then scheduling Star Trek results in less profit for CBS unless Star Trek can make more money than CSI.
Your statement is correct, yes, but why would a new Trek series have to replace one of CBS's flagship shows? Instead of Trek taking the slot of CSI or BBT, Trek would take the place of one of the under-performing shows (such as "We are Men" or "Hostages" this season).
Trek wouldn't have to make more than the top-performing shows, just more than the show that it does replace, which it could likely do easily.