I was in the used/rare book business myself for over 25 years and I agree about the values. Funny, while my wife and I were in a couple of thrift stores this afternoon I ran into 2 different guys book scouting. Nice to chat with someone who knows the business!It's been several years ago, probably 8 to 10 years. Any copy that came up on ebay went between 250 and 500 back then.
Used/rare book prices fluctuate like every other thing that people collect. I've been in the book business for about 20 years now. Some books hold their value well, others don't, and some bounce around like a yo-yo.