Scott publishes new listing for stamps still on sale by USPS. For example, the new 2016 American Landmarks LaCueva del Indio, face value $6.45, is listed as a value of $13.00 by Scott. The basis has been to just mark at 2x face value. Scott states their values are retail: "an amount one would expect to pay for a stamp in the grade of Very Fine with no faults". Scott prices based upon auctioneers, published dealer price lists, etc.
So, how did the $13.00 get determined. Scott is making assumptions for a "dealer" (they do not define dealer). The dealer of 1989 (the first year revalued everything) is different than now and more are selling person to person through places like
ebay. They claim to use published dealer lists, etc. but that is not where all the stamps are sold.
When they make the assumption of 2x face for initial value they are making accommodations to dealers. In the above example, if a dealer has fixed costs, I would expect it to be fixed amount over face not 2x.
It is sort of a game since some dealers very often say SCV $x, priced at $y (often well below SCV) to imply a bargain. Others use Brookman to make the percentage even higher. Some dealers revolted back in 1989 since the "value" decreased and shows how Scott can influence market prices rather than just report the market prices. It is interconnected.
Dealers often sell using SCV and Scott bases upon dealers...kind of a circular loop. Only when a specific item has much higher demand does the price change such as one a particular issue (like topical issues) or like the Jenny has a lot more interest than general ones.
Thanks to
ebay and other outlets, we see the true economy that is not reflected in retail catalogue prices and people are always surprised that when they try to sell their collection they will get a very low percentage of catalog...like any collections with post 1940 material.
For modern material,I find it nearly useless since you can get many issues including high face plate blocks at face if you wait a few days and you do not need to buy $100 work to get a collection to get one.
Al