Everyone has made mention that this is an excellent book to get for rules and goodies, but is there anywhere I can get a copy of this still (PDF or physical) without paying $100+?

As far as I am aware, the only legal outlet for 40K-RPG PDF's was DriveThruRPG; which pulled every title when FFG lost their license from GW.

PDFs will be available soon again through the new holders of the license Ulisses Spiele.

However the print was out long before the license was gone, so good luck finding a copy cheap.