You're probably looking at over $1000 for an ACOG. Somewhere around $1500 if you want the whiz-bangs and doo-dads. I know, it's awfully expensive...but just about everyone that has one swears by them.
Elcan...depends on the model. I don't think that any of them are cheap, and you may be looking at up to $2000 for the top-end Spectre DR. Wolverine carries them.
I had mixed experiences with Elcan scopes when I was in the military, but they are a good quality scope with good optics. Much of the problem with the Canadian military Elcans was due to the constant use, misuse, and abuse that the scopes and the rifles (and LMG's) that they were on suffered. Also be aware that I was using the first generation of Elcans that got widely issued to the CF, and I think that they've improved their mount system since then. For range use, or bush use by someone who actually gives a d@mn about their gear, an Elcan might be just fine. That said, I hear that many of the guys deploying on recent rotations to Afghanistan are purchasing Eotechs or ACOGs to use instead of the issued Elcans. Any of the guys currently in uniform (or PMC's) care to comment?
As other folks have mentioned, it depends on what you are doing with your rifle. Only a few optics will give you the combination of 1X "red dot" type performance as well as 3X/4X for longer range use. Unfortunately, these are the pricy ones...most of them will cost significantly more than the rifle itself unless you get an incredible deal.
Lots of good info here!!!!
http://www.canadiangunnutz.com/forum/showthread.php?t=31083