Quoted from psyched123:Online stores? I came across Monkey Arcades which seemed to have good prices with free shipping.
From doing a little research, Monkey prices their pins and then through connections gets the pins for you they do not have in stock. So you are probably going to get a middle-mans price. Never have dealt with them, so cannot comment on their service, and maybe they have changed how they acquire pins. Here is an old link from RGP that talks about them:
http://groups.google.com/group/rec.games.pinball/browse_thread/thread/4c148f602bbc4954/ed678a4988e0bbff?hl=en&lnk=gst&q=Monkey+arcade#
If you are going to the retailer route, I would suggest Little Shop of Games. IMO, he has nice prices and his machines are nice players. Easy to deal with. I've bought a pin from him and my buddy has bought 2.
As mentioned before, networking is by far the best way to get pins. I'm constantly passing on info from other pinheads about things they want to change out. Remember retailers have overhead, (mortgage, employees, utilities, etc...)
Ebay is usually higher as people use it to draw customers to their off website, or use the "Best Offer" to sell off of Ebay. The best way to get a good deal off of Ebay is to contact the seller and ask how much would it take to end the auction early. That is why you see a lot of auctions ended early with "item is no longer for sale" at the top.
What part of the country are you from? Shipping can play a big part in pricing as getting a pin from the East to West coast can run close to 500 extra. Flip side, you don't have sales tax a lot of times if out of state.
Other places where I have gotten deals, or seen deals: (compared to retail online sites)
Pinball Classified (Mr. Pinball), Pynball.com, posting WTB on websites like Pinside, RGP, The Bash, Klov,.
Go to a pinball show. In California, PAGG, CAX, and PPE are great ways of meeting people and getting games. Go early and bring cash. I did not see this mentioned yet. People bring games not only to support the show, but to trade and sell. I've also meet a lot of people there that grown to become pinball friends.