Have you ever wondered why price guides are so different? Papermoneyguide.com values a GEM 1938 $1.00 at $45 while it books for $145 in the Schwartz/Lindquist book. Now, I can see a little difference but one guide being 3x another?
I think it has to do with what data they use to derive their prices. better data = closer (to true) prices
Also, the latest edition of S&L is, what, six or seven years old now? Could just be that prices aren't what they used to be....
It's seems to me that the currency market will wax and wane on prices. I always recommend that if you are in the market for a particular Fr.# to check the sold prices on eBay and Heritage to get a sense of the current market. Price guides are just that, a guide to prices at the time of printing.
Registry set mania puts an increasingly disproportionate premium on notes that are labelled 65 EPQ or better by a TPG. Notes that only get called MS 6X PPQ, or even worse less than MS 60, have been selling for less and less as a result. Pure hobbyists who are working to complete a collection can benefit handsomely by rummaging through the scraps. Some of my favorite notes show the effects of having served their function for a little while. And I paid a fraction of what I would have had they spent most of their lives in a vault.