A lot of sellers will not accept PayPal for large purchases because of fees and/or disputes. What is to keep the buyer from opening a dispute. Cash in hand, bank transfer but once it's transferred it's gone or possibly an escrow service. Best advice is get to know who you are buying from and check out the reputation of the seller. Also PayPal places a hold on the money which can be a pain for a seller of they are looking to turn around and purchase something else.

Also shipping isn't cheap, so in terms of getting the machine back in a dispute you could be out a small fortune in shipping charges.

In terms of reputations on mr pinball, post on the forums for folks who have dealt with the individual before, google them and call them and talk on the phone. If you are at all uneasy do not buy from them. You can also ask a fellow pinsider who is local to check out the machine for you.

Another thing to remember if you sell a couple machines in a year at the current prices and use PayPal you could fall under some new IRS rules

http://thenextweb.com/insider/2011/08/16/new-irs-rules-require-paypal-to-report-sales-information/