Many people prefer to buy their pinball machines at auction. Buying a pinball machine at auction can be an interesting experience.
Here are the two main arcade auction companies servicing the United States. Both companies have auction calendars so you can find out where they will be in the near future.
United States Amusement Auctions
Here is a list of items you should consider taking to auction, built off a post to rec.games.pinball, the definitive pinball newsgroup.
There are a few precautions to take before buying at auction:
Keep in mind, you will likely be bidding against the owner of whatever machine you buy. It is not against auction rules for sellers to bid on their own auctions.
You will pay a "buyers premium" on top of the price of the item, and will pay extra for using a credit card. If you have questions on the amounts, you should ask the auctioneer's staff before bidding for clarification. Often times, this can get up to 20% of the bid price, making that $1,000 bargain pin not quite such a bargain at $1,200 total.
Make a list of which items you want to bid on, with some notes on the condition and your maximum price. If the pin reaches your maximum price, stop. You can make a semi-educated guess of what pins have been going for by looking at Mr Pinball's auction price list (hasn't been updated for awhile), or by searching on Indianapolis Auction Results at http://groups.google.com, group rec.games.pinball. It's always hard to keep this in mind, but there are very, very few pins that had a super low production run, and those won't be at auctions, they'll be in collections.