Vagaries of Air Fares

I have been researching air fare options for a possible trip to the Russian Far East this summer, and am amazed by the range of prices on some of the usual cheap fare Websites (www.travelocity.com, www.expedia.com, etc.)
For a trip from Montreal to Vladivostok, the eastern terminus of the Trans-Siberian Railway, the prices quoted range from a little less than $2.000 to more than $11,000. Because I would actually be coming back from Ulan Ude to Vladivostok, I would probably have to add quite a lot more for that flight, which I am guessing could be via Moscow far to the west. (In Russia as in Africa, sometimes you have to fly very much out of the way to get where you really want to go.)
Then there are round the world air fares to consider--haven't had the energy to look into them yet. I did check whether I would save much by using my Aeroplan (www.aeroplan,ca) points to Japan for the trip out, then returning via Moscos, but that didn't seem to save anything.
The difficulty with the fare that costs less than $2,000 is that you are 29 hours in transit, and any delays would of course add to that sum, not to mention getting to the airport two or three hours in advance. It would make for a very exhausting day and a half or so, I suspect.
Situations like these are ones where it may pay to use a good travel agent and absorb the extra fees, I suspect.