The silver strike machines usually have symbols like single, double and triple bars, sevens, and cherries. Some combinations award credits (coins) and some award 1 or more strikes. I've never seen one that awards both strikes and credits for the same combination. I have seen some that only award strikes, or a free pull for other "winning" combinations that don't award strikes.

At any rate, I think it's one of the attractions to strikes when they can only be won, not purchased. I've had strikes cost under $7 each (3 for $20), or $40 to win one, then sell the stupid thing for $20 <g>! It has averaged out for me that I haven't lost money over all. But then I'm not big on strikes.