I've over paid for a few of my ponies too but I still have every one of them because it was worth it to me at the time. I probably shouldn't have paid $102 for my mountain boy lightening though since he's only worth about half that:/
I have sold a few ponies that ended way over what I had expected them to. The two main ones people bought that surprised me were $150 for a near mint white Glory and $41 for a mint flutter pony Lily with no wings or accessories.