A Handwritten Typo?

I walk into my friendly neighborhood bagel shop this morning when I noticed someone posted a for sale notice for a car. There were two pics if a sharp looking old car. The handwritten ad said it was a 1965 Valiant and they were asking $300. The pics looked great, and there was no way I could be reading this wrong, "$300" can be read only one way. So I called my bro-in-law and left him the details. He called and as it turned out it was a typo. They didn't want $300, they wanted $4,500. How do you make a mistake like that? Plus it was a slant six. Who's going to buy that?