There was about 30 seconds left on the auction and no bids had been placed, so I bid on it and got it for less than $20. The buy it now price was over $40. Did I get a decent deal or was the BIN price ridiculously high? Sorry for the photos, I just won the coin about an hour ago and these are the seller's pictures.
I would say that it would largely depend on variety, and how the surfaces look. If it's not a rare variety 20 bucks might be at the higher end of average for this coin. Now if it turns out that the coin looks nice and it is a more rare variety, you could do okay. I would need much better pictures to attribute it for you.
Assuming its a regular 1851 large cent, the BIN price was ridiculously high and for $20 its not a bad deal. Maybe a few dollars more then the regular price but if you like it and are keeping it then you did just fine
i got one in better condition than that for $3. (in 2007 when i was 9 years old ) you probably paid what its worth, $40 is too much
IMHO: $10-15 would a fair price. I don't think you took a bath on it by any means. $40 is ridiculous.