I am not aware of a recent catalog for US coil stamps and leaders. I have hundreds of them now and have assigned values in my group based only upon my own casual observations of market values.
The following is my opinion in regard to values. First, leaders have a greater demand than trailers and therefore leaders can bring about 50% more then the same issue on a trailer. I collect and present them as pairs whenever I can, even if they are not 'matched'. (In other words, the leader and trailer were not originally together on same roll.) For me, I am willing to pay a premium for matched pairs (25% or more).
I also think that the number of stamps on a leader or trailer can increase the market value (more stamp = more value).
Also note that there are a number of differences between the leaders. Leader paper types and the imprints can influence the market values. The 1938 Prexies for example, the early printings have manila paper while the later printings are a white paper. There can be a number of differences on the imprints included fonts used, and most certainly the roll size. For example, in my experience, leaders marking a roll of 500 stamps tend to be the most common. Leaders from rolls of 3000 and 5000 are much less common for most issues. But these imprints are something that many people have little knowledge so
ebay listings tend to not reflect a lot of value difference for these collectibles.
Lastly, any partial leader or trailer on cover demands a significant premium. Many of the more common ones can drive the price of a cover to the $75-$100 range.
Don