It's not a scam, you should get out more often. They usually put the dollars in between quarters, so you still need to hit off the quarters and not just the dollars.
Actually these things are well known scams. They even mentioned it in the article I posted a page back. The thing with the dollars, they are probably weighed down with the coins, of course, but there's a variation of ways they rig the games.
Here's the relevant quote from the article:
Brnovich said that, in the case of many of the machines, it's not even like the customers got a fair shake.
“It appears that these devices were not only illegal but that many patrons didn't even have a chance to win the prizes that were offered,'' he said.
The Attorney General's Office said that the machines actually cheat customers because they have hidden compartments: Some of the coins that fall into the bin never make it to the customer but instead remain in the machine.
“These devices are a fraud on the public,” Attorney General Terry Goddard said in a prepared statement. “They are built cleverly to deceive the player into thinking that coins or other valuables are about to fall into the > collection bin as winnings, but players can't see how they really work.''
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