I've permanently reduced the price of many of most popular modern d20 books that are also in print (with the only expect being DW: Survivor's Handbook). Most of the books are price from $5 or $10 now, with the prices of the print books the same as PDF.

Also, if you own some of these books already, the upgrade price is now only $1.

RDP is also participating with some of their print books.

Here's a list of the books with price cuts:

$5 print / $1 upgrade
The Foundationists $5 print / $1 upgrade
Modern Backdrops $5 print / $1 upgrade
Metal Gods $5 print / $1 upgrade
Legends of the Samurai HC $5 print / $1 upgrade
Blood and Relics $5 print / $1 upgrade
RDP: Alien Invasion $5 print / $1 upgrade
RDP: Blight Elves: Architects of Despair $5 print / $1 upgrade

$10 print / $1 upgrade
Legends of Excalibur: Arthurian Adventures $10 print / $1 upgrade
Blood and Fists: Master Edition $10 print / $1 upgrade
RDP: The Blood Throne: Survivor's Guide to the Age of Blood $10 print / $1 upgrade

While the price cuts are permanent, the print books are limited depending on the title.