Audiogon is an alternative to ebay.
How much Do I think its worth? I've had my eye on them on ebay I would say about 2000 USD +/- 500 depending on condition box etc..
My personal opinion is this: economics 101 supply and demand; what is something worth?
well its worth what somebody is willing to pay. You can ask whatever you want for something, but your not going to sell it.
the 1200-gld is more rare than the LTD but in all honesty it is just a gold M5G like the LTD is just a gold M3D.
Its only going to appeal to a small sector of technics 1200 fans.
I really believe the true measure of somethings worth its price at auction and even then there can be large variations.
How will the price evolve? Rubbing my cristal ball

I would say will probably remain stable perhaps slighty above inflation.
Seriously I'm just guessing...