What are the effects of different types of rear shock installation on full-suspension bikes?
The good folks at Bike Radar have already covered this in pretty good detail in a two part article:
Part 1 and Part 2

There's also a chunky thread on the Pinkbike forums that has pictures and descriptions of loads of different setups:
Pinkbike - Basic Full Suspension Types / Reference With Pictures

In regards to price, it is not the suspension setup making the difference, it is the quality of the components.