I recently did an analysis of some Scott catalog prices in their graded listing. I was curious about pricing trends based upon condition. This is by no means an extensive analysis but found the data interesting.

One motivation on understanding the relationship of grade to price was because many dealers will quote a grade and catalog price but for many stamps Scott does not provide a value in condition. You can see a collection where the description may be noted as "mostly F-VF NH" but then the seller attributes a catalog value. They will then list a selling price. Some ebay sellers will show a damaged stamp but still reference the Catalog value.

Many sell at 30% of catalog but condition is not really considered as a variable.

I took some Scott values for some airmails then used VF as the standard and normalized all values based upon the VF price.

I did see some trends with more exceptions at the higher grades (Superb).

If the trend was as my predictor row shows a mostly F-VF NH collection is worth around 75% catalog so the dealer selling a F-VF at 40% catalog price is more really closer to 50+% when condition is applied.