A 50" Canadian is a huge moose. They are out there, but you had better be ok with eating your tag if you plan to hold out for one that big. 40"-45" is a good, mature bull in Alberta.
I hunted with Misty River out of Fort Mcmurray three years ago. They have a fly-in lodge hunt in a remote area with low pressure. They manage their area for age class. They have either taken or seen a few that big, but they are rare. Most of the bulls that get killed are in that 40-45 range. Bowen Lake Outfitters is active on Rokslide, and they also kill some big bulls in remote areas in Alberta.
If I was dead set on 50" in your price range, I would go to Alaska DIY. If you need to go guided in Alberta since you can't find a hunting partner for AK, just adjust your trophy expectations down a bit and go have fun.