Was the show making money five years ago? Ten years ago? (Hint: if it wasn't, it would never have made it to its tenth anniversary.) Was Letterman's show making money for 22 years? He was also leasing the Ed Sullivan bldg. The problem isn't the cost of that lease (unless CBS raised the price astronomically recently) or the amount of staff, it's that the advertising market for network TV has virtually collapsed. I agree the show's likely losing money, but call balls and strikes fairly. Colbert doesn't sell the ad time on his show, that's CBS. If they can't sell enough ads -- and the OTA end product doesn't support that assumption -- or they can't get their price and have to cut deals to fill the time, that's also not Colbert's making. Not when they're trying to sell the top-rated late night show.
Maybe, ya think, maybe they should rethink the strategy of giving away the product on Youtube? Out here in California, I get to watch Stephen's (and the Jimmy's, and Seth's) monologues hours before they air on the local stations. What's my incentive to stay up past midnight to watch it OTA?