Proof Coins / Proof - Mint Sets

The errors for 70/80/90s are too numerous to list, need to research.
The link below is to the site with a wide range of information.
http://www.varietyvista.com/index.htm

It seems what you are asking is why some proof coins go for more money than others. These are all coins that are pulled from proof sets but have exceptional value for some reason.

As previous posters note, some high prices are due to errors.
Another reason is that some proof coins are made by chance with better planchets, have better strikes than their peer coins of same issue, or have other attributes that set them above the rest of the pack of same issue (exceptionally clear fields, deep cameo quality, etc.) People who recognize these qualities send the coins to well known grading companies to get them certified for grade which adds cost and value. So, when looking at higher priced proofs, check the grading. MS or PF 70 grades command the higher prices.

Thank you for the answers....I am going to have to research what to look for in finding the better made proof coins before going through all the sets I received and see if I have anything interesting in there.

Again, thank you