Years ago MastroNet had a somewhat peculiar bid choice enter method, and I remember near the end of the auction I accidentally placed a bid with an extra digit. Think $50,000 instead of $5,000
For the record, there were no competing bids placed after that.
As far as paying too much and all that, learning from one's own mistakes is an integral part of learning. As I say, Fred Astaire probably tripped and fell many times when he started out. That's why I also tell beginner's to start out with small purchases. Buying a $20 reprint is a useful learning experience, while buying a $10,000 is a tragedy.