I picked up Quake 3 for Linux for $15 (Canadian) at a local software shop, along with Railroad Tycoon for Linux for my wife (also $15 Cdn). We haven't had time to install or play these games. The Quake 3 packaging is really nice; it comes in a tin box.
However, these games were ported and published by Loki Software, which went belly-up some time ago. I bought the last copies of each game from the above software shop (Multimedia Technologies at Broadway and Granville here in Vancouver, British Columbia). I was pretty happy with the find; I feel like the Quake 3 package is like a collector's item