We found 2 Reddit comments about Sensation and Perception, 8th Edition. Here are the top ones, ranked by their Reddit score.
The perceptual psychology class required us to get the 8th edition of this book. The cheapest I could find it, after some internet sleuthing, was $70 or so for a used copy... but as you can see it costs $160 new.
Instead, I got the 7th edition used for $8
The semester is over now and I made it through just fine with the older book.
And that is how college textbooks work :)
This info is from a Sensation and Perception class. I can link you to the textbook. http://www.amazon.com/Sensation-Perception-Virtual-Manual-CD-ROM/dp/0495601497/ref=sr_1_fkmr0_2?ie=UTF8&amp;qid=1323450129&amp;sr=8-2-fkmr0