I think people are confusing the mass which appears on orbit with payload. Payload is (as meant when the word "payload" was created) rather the goal; in case of

I think people are confusing the mass which appears on orbit with payload. Payload is (as meant when the word "payload" was created) rather the goal; in case of Saturn V it was Apollo stack which needed to be launched to the Moon. Similarly, in Space Shuttle case payload is something which is in the shuttle trunk; that's why typically a shuttle flies. Illustration for why 140 tons isn't the payload of Saturn V is that Saturn V wasn't able, or designed, to launch arbitrary 140 tons to LEO, and Skylab is a implicit confirmation of that. The definition of payload to LEO in case of higher-than-LEO missions can include booster stage and fuel, but then we have another strange case of Shuttle with IUS - the payload could fly higher, and was rather small, yet we don't consider Orbiter's mass as part of LEO payload in this case. Since, as another consideration, we usually consider Saturn V as a 3-staged rocket, not a 2-staged (as flew with Skylab) with a space booster stage which is used for LEO insertion as well as for subsequent translunar injection, it would be logical not to include 3rd Saturn's stage into LEO payload. Then Saturn V LEO payload becomes too small to be meaningful (TLI requires a lot of fuel). It would be better - here - to consider Space Shuttle LEO payload to include Orbiter's mass - that justifies large liftoff weight. As for what's Saturn V LEO payload, this question is better be met with clarifications.