Vid... no matter what website you use for your tickets, it always depends on your travel dates.  Adjust your dates a little with expedia and you'll notice a significant drop in price. 
 
The bitch is that sometimes the connections are really messed up.  In my experience, the best route is Montreal - Chicago - Las Vegas if you can get it within your budget.  Don't connect in Atlanta.  It makes your itinerary a whole lot longer. 
		
	
		
		
		
		
			
		
		
		
		
	
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