CT Art

I keep hearing and reading more abou this CT Art chess program.

I have read and reread 400 Points in 400 Days, and after trying it for a while, abandoned it. Now, upon reading everyone's success with it (mostly on web logs), I am trying to get back into it. The tactics part seems the most crucial and the book highly recommends this CT Art program for helping budding students learn tactics. Hence I am looking to buy the CT Art tactical chess trainer for my computer. I found some copies online for about $28.00, but that seems a little high for me.

Any ideas on where I can get a cheap copy?