Three lawyers and three accountants are travelling by train to a conference. At the station, the three accountants each buy tickets and watch as the three lawyers buy only a single ticket. "How are three people only going to travel on one ticket?" asks an accountant. "Watch and you'll see", answers a lawyer.
They all board the train. The accountants take their respective seats but all three lawyers cram into a restroom and close the door behind them. Shortly after the train has departed the conductor comes around collecting tickets. He knocks on the restroom door and says "Ticket, please". The door opens just a crack and a single arm emerges with a ticket in hand. The conductor takes it and moves on.
The accountants sees this and agree that it is quite a clever idea, so after the conference the accountants decide to copy the lawyers on the return trip and save money (being clever with money and all that).
When they get to the station they buy a single ticket for the return trip. To their astonishment the lawyers do not buy a ticket at all. "How are you going to travel without a ticket?" says one perplexed accountant. "Watch and you'll see," answers a lawyer.
When they board the train the three accountants cram into one restroom and the three lawyers cram into another one nearby. The train departs and shortly afterwards one of the lawyers leaves his restroom and walks over to the restroom where the accountants are hiding. He knocks on the door and says, "Ticket please".