Hello Sheitert,
Welcome to the monkey house. I don't subscribe to Blue Book, but it might be of limited use here. The price of desirable vintage tables seems to be dictated by availability and demand for a particular model. One thing is for sure, they keep going up, especially in the past few years.
For those not familiar with the 1100, it's here:
http://www.thevintageknob.org/technics-SL-1100.htmlPerhaps you're a collector and want this particular model, or maybe you've decided that this would be a good table w/a different arm. The 110 arm doesn't really look to be up to modern standards. Any example has to be at least 35 yrs old. I suspect many have fallen by the wayside by now. The going price is whatever one can get. The one on Agon is a piece of furniture and is overpriced IMO. There is/was one advertised recently for $450. I'm not sure if it's a good value, but that depends on why you want it. It looked to be in very good condition.
If this is for general use, you might want to consider something like a 1200, SP-15 or various models by Kenwood or JVC etc.
neo
