It is common knowledge that when buying anything second hand it will be cheaper and, "not as good as...". used arcade games may be the exception to that rule. With used arcade games, if you do your homework, you will be able to find top quality equipment for at least one half of the original price.
Naturally, factors such as the manufacturer, the age of the equipment and the condition of such are all things that will affect the pricing one way or another. Other factors include the need of the seller to dispose of the equipment.
Used arcade games may be sold individually or, in lots. There is no number limit for lot sales and these may range anywhere from 10 to "you name it". Once again, depending on the seller's sense of urgency, you may find great discounts when buying "in bulk". Other sources of sellers and buyers of bulk used arcade games are establishments such as Chuckie Cheese, who are smaller than the larger carnivals yet have a considerable amount of these games.
How much will it cost you to ship is another factor which you must consider in the used arcade game purchasing equation. Modes of transportation, nationally, include truck, train or air, with air being the most expensive.
Brokers are a great source of information and contacts regarding used arcade equipment. With literally hundreds of connections, nationally and internationally, they will help you find what you are looking for. Also, brokers are able to cop deals such as a "no packing charge" when purchasing a certain minimum number of these games.