t206.org valuations?

[camlov2]

I was trying to find values for t206 cards and having a really hard time. I normally use ebay completed listings to get a ballpark price for cards (works well for topps/bowman) but since t206 seem to have so many more variables Player/Pose/Condition/Back, this method doesn't work very well.

I came across the valuation feature on t206.org and wondering what opinions collectors had with regards to the prices given.

Also I have a question regarding how to grade cards that appear to be trimmed or have back damage.
To pick the very first card alphabetically here is an example-
Abbaticchio (blue Sleeves) Piedmont 150 factory 25

Poor $13
Fair $18
Good $20
VG $25
VG-EX $38
Ex $63

If you have this card that Grades VG-EX but paper loss on the back how would you suggest grading the card, do you reduce by multiple grades or always drop to a certain level?
If it appears to be trimmed would you drop the value the same way or differently?