This is a major difference between buying pinball machines "back in the day" versus buying games today. Back in the day, whoever messaged first usually was given a chance to see the game (or inspect detailed pictures) and have a discussion with the seller before making an offer. Today, however, with people rampantly throwing money at the pinball games, you basically have to commit to buying the game at full price without even knowing what you are buying (which honestly, flat out sucks). The only recourse is to back out on your word to buy the machine in the event that the game is a litter box (which you would have known had the etiquette of days past still been in play).
When I sell a game I try to maintain that whoever messages first gets a chance to have all their questions/concerns answered. If I have a lot of interest, I will sell to the first person that offers me my asking price, but will always give that opportunity to the first responder by saying the price is firm if I feel I am destined to get my price due to the amount of responders.