How do you value multiple mint errors and mint error/variety combination?

Recently I found myself gravitating toward mint error coins. I just think they are really interesting.
As examples how do you value the following?
1- straight grade with two mint errors
Example: Lincoln cent pcgs ms63RB mint error; die cap/brockage
2-details grade with a combination variety and mint errors
Example: 1945p Jefferson nickel pcgs vg details mint error; reverse lamination, variety; DDR FS-801
4
Comments
My opinions:
Coin #1: An interesting and very visible error. Worth a premium but not as much of a premium as an obverse visible coin would bring.
Coin #2:: Melt value. Laminations are a major negative. A microscopic DDR can't save it. If you can find someone who thinks it is cool and will pay a premium ... take the money and run!
Laminations on war nickels are very common. Someone looking for this variety probably wouldn't want this coin.
Keeper of the VAM Catalog • Professional Coin Imaging • Prime Number Set • World Coins in Early America • British Trade Dollars • Variety Attribution
Did not pay attention
Young Numismatist • My Toned Coins
Life is roadblocks. Don't let nothing stop you, 'cause we ain't stopping. - DJ Khaled
The details grade was probably for it being scratched.
Keeper of the VAM Catalog • Professional Coin Imaging • Prime Number Set • World Coins in Early America • British Trade Dollars • Variety Attribution
The 45-P DD FS-801 5c is not a microscopic DD. It's not particularly rare, but it is a nice DD.
Remember that my comments are my own opinion. I look at the photo and see nothing of any interest. I'm not buying into the whole minor double die hype that seems to be present in today's coin market.
There is absolutely NO FORMULA. Errors are valued based on rarity and, often to a large extent, eye appeal. Combining two errors makes the rarity greater but the pricing really depends on what the "wow factor" is and what the errors are.
For the two examples shown, the valuation would be very different. The die cap with brockage is scarce and wow! The nickel shown would have very little value to many people with the VERY COMMON lamination actually lowering the value for many of the people who would collect the DDR variety.
There's a thread here somewhere about errors on key date coins. Go read that thread. For many people, the error is a + (depending on the error) for others it is a negative because they care more about the key date.
All comments reflect the opinion of the author, even when irrefutably accurate.