Buyers (spendthrifts like me) beware: if you click on the illustration of Lovecraft by David Levine, the NYRB website will try to sell you a nicely matted and framed version. _Then_ they hit you with the price!
Stating the obvious, the only reason that fancy Solar Pons Omnibus is $125 (and that's low for really good condition copies) is because it was a limited edition, is out of print, and in the collector's market now. This was a beautifully produced prestige edition, slipcased, two volumes, 1306 pages -- not meant for the casual fan. Obviously books like this rise in value, sometimes astronomically, when they go out of print. The Solar Pons paperbacks from Pinnacle Books are fairly easy to find and not expensive at a few bucks each. Ebay often has them.