LGA-YVR comes up with $110 per person in fees if you fly United, $150 if you fly Air Canada.
If you fly LGA-SEA instead, you're looking at $33/person - though that's shown as a $12.60 "US Passenger Safety Fee" and a $20.40 Airport charge, so I'm not sure how that would get lower.
The savings from the SEA routing would almost exactly cover 4 Amtrak tickets from Seattle to Vancouver, round trip, and it's a nice, scenic ride.