How much does a Mint-made flaw reduce value?

BIGAL2749

At a show in Albany NY yesterday I picked up a back issue of Coin World which had an article on some of the Mass Silver sold in the Kendall Collections. The author Steven Roach, wanted to highlight three different examples from that auction and when I looked at the first coin discussed I immediately recognized it as the same variety I own. In fact it was the coin that got me back into coins after a 5 year break.
ANA show was in Boston that year and future son-in-law wanted to go to a major coin show.
I'm a sucker for luster and when I saw the coin in Chris McCauley's table, I wanted it. The Mint-made flaw is apparent and too bad it's there but having collected early type, adjustment marks (short of defacing the major devices), planchette defects, and strike thrus do not bother me that much. However I know it does to others and I've always wondered what magnitude of discount applies to the flawed coin.
These two are graded the same (different service) and would like to get some opinions from the members. BTW the author mentions the luster on the Kendall coin and it was luster that sold me on mine coin as it rivals mint state coins.

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