$100, you got off lucky. I had $80 in my checking account, and bought something that was $70.68. Yes, I remember this amount exactly, I'll never forget it. PayPal double charged me, charging the debit card associated with that account, and the actual bank account. So, I overdrafted. The bank charged a $35 fee, but didn't pay the charge, which is standard practice there. So, PayPal, without ever notifying me, and the bank never notified me for over a month, tried to process this charge EVERY DAY for 38 days, at which point I only found out because my monthly statement was in the mail.
Yup, a $70.68 purchase that I had the money to cover in the first place, ended up costing me $1,471.36. Yes, that is $1,471.36. Now, my local bank had zero sympathy, and despite the fact they should have notified me about this, wouldn't reduce the fees one cent, and required me to pay it off within 45 days. Being a broke college student who doesn't have a job while in school, I was screwed. Of course, they were happy to give me a loan for $1,515.50 (3% processing fee.) So now, for a damn text book for school, I paid $1,515.50, which will be even more after you account for interest.
Lessons learned? NEVER use a local credit union, they're useless idiots. I closed my PayPal account and will never use them again. I also had every bank do a complete block on PayPal, who knows if there will be some mysterious "ghost" charge from my closed PayPal account, I wouldn't be surprised. So while I have sympathy for your $100-$10 purchase, it could be much, much worse.