Quoted from mof:
You seem to think some may have a reason to not want to sell games? I'm lost...
When you walk into Pinballz right now, there are hundreds of different games and machines to play, some redemption, some arcades, some pins. Most of them will have a price tag on them but it's always insanely high. SM has a price of like $7,995, MM with a price of something like $16,995, and even a Kiss with a playfield that's worn to the wood is listed for $3,499. These games are what attract people into the building, and people will dump their quarters and tokens into the game (thus making money for the business owner.) If all the games actually had a decent, fair price on them, people would purchase them and take them home.
Now imagine all the A list and B list games were bought up. Suddenly when you walk into the building, there are hardly any good games to play. So you walk around a bit deciding on what game you want to play, but you don't want to play anything since all the good games are gone. You decide to just go home and not spend any money at the business. You tell your friends, and slowly word gets out that all the games are gone and no one shows up anymore.
If the business owner sold all his games at market prices, he'd probably have a good chunk of change no doubt. However, there is no more money coming into the business each day, so paying monthly bills gets harder and harder when the large chunk of cash you had from selling everything gets smaller and smaller. There's no more growth.
So ideally, the owner wants to keep as many games on hand as possible, it brings in more customers. But if someone wants to shell out $5,500 for a Gorgar, he's going to sell it, he'd be crazy not to. Then he can take that $5,500 and buy the newest, latest, and greatest Stern, JJP, Heighway, or Spooky game which will bring in more customers, and certainly get more play than an older Gorgar.
To wrap it up, he doesn't want to sell his games, because the games themselves are what bring people into his business, and it's how he can continue to grow as a business. But if the right buyer comes along and wants to spend three to four times the amount than what the game is really worth, you bet he will sell that game in a heart beat.
(Plus what jayhawkai said, but he put it more eloquently)