www.abebooks.com/ and others
1. If you know the author, sometimes you can find a book or deck somewhere in a different area, even a different country for a reasonable price. I never found a Folchi or well-known tarot artist or author for a less expensive price, but the smaller press versions emerge in used bookstore listings.
Used bookstores or friends that haunt independent 'metaphysical' or 'used' bookstores in certain areas can yield finds. A local used bookstore yielded a 1980's reissue of Tarot Balbi, a Marseilles variant, and a black and white pop tarot (20th Century) for less than $10.00. I found a French translation of the Oswald Wirth's book and the majors reissued in an anniversary edition for the same price...but this is over eight to ten months of looking periodically.
2. From a Minneapolis friend: they had a few oop European (Masonic/Ashkroft-Norwicki's Shakespeare) tarot kits for about $25.00 earlier this year:
http://www.magusbooks.com/main/
3. Gerbear meantioned the Bodhi Tree bookstore, which my sister took me to when I visited her area. Also in Southern California, at least last year, a small retail chain in California called the Psychic Eye had stores in San Francisco, Mountain View, and one or two down in the coastal cities...Redondo or Hermosa Beach?
I don't know if it still exists, because one of the local Northern Cal stores closed...and they used to carry AGMueller titles. The area code was 310 if you live in Southern California...
4. Sometimes local Borders, Barnes and Noble and regional bookstores carry artists and authors titles...Guardians of Wisdom is regional to Monterey, Ca., for instance...but it can be luck of the draw.
I found a very funky, not especially recommended "Love is the Earth" tarot is regional to some of the Southern Cal beach cities. The box had the best collage samples on the cover. It was very lucky for me that someone had a sick friend who liked that sort of thing, because it wasn't worth the weight it added to my luggage, for me.
Happy hunting, hope some of these yield finds!
Mari H.