1. Pauli's line-up - Two pinball machines cannot occupy the same space, in the same line, at the same time. This is regrettable, and leads to collectors endlessly needing more space.
2. Newton pass-off - For every pinball machine, and pinball part, there is a collector that wants it.
3. Inertia of the Deal - Once a pinball deal is set in motion, the deal will inevitably end. You may not like the results, or get what you wanted, but the deal will end.
4. Conservation - The number of pinball machines reaches a relative constant. Pinball machines may change hands through time, go from game room, to game room, but the number stays near constant.
5. Schrödinger buyer's remorse - All pinball machines you buy will look better, until they become yours. Once they are yours, you have opened them up, and will see only their warts. The cat is dead, and you must deal with it.