I'd say the author means that Tom did more work scamming his friends into whitewashing the fence than he would have if he had just done the job himself to begin with. I can't say I agree. If you read the actual story Tom ended up with a lot of loot and a fence with three coats of whitewash and did almost no work himself.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.