I have had the larger charge show up on my account right after using it while it was pending, but charged my account correctly when it posted.
I also have never had this problem. I ran many machines at a time and at the end my card shows all my swipes added up. For the full afternoon washing it was $37.00 not $3.50 here and $2.50 there.
I haven't had this problem before and I've gone plenty of times. Have you checked to make sure you haven't done any settings that would make the price change (washer)? Or take longer (on dryer)? If you're worried, you could mention this to the owners. They're usually at the desk whenever I go in. I'd tell them your concerns
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