Chuck,
The Magne-Matic from Micro-Trains and the Accumate work with the same uncoupling magnets. Accumate has basically copied Micro-Trains design. The under track or between track magnets from Micro-Trains are the industry standard. You can also employ the Rix hand-held magnetic uncoupler, but this involves the old 0-5-0 hand switcher to actually move the car you want uncoupled. For true hands off uncoupling, go with a track mounted magnet.
As for your mentioned pricing, it all depends on which coupler conversion you are buying. Different conversions have different prices.
You might look into the MT web site at
www.micro-trains.com for info on their operation. Other than that, you could fill a library with coupler information alone. Your best bet is to visit a hobby shop and do some personal on site hands on research. I do not know of any specific articles on different types of couplers, but there is always the Google search. Try it.
B-)