yes it is cheaper to fly to Seattle. - but there is the added cost of a rental which you don't need on arrival and might even have to pay extra to park if you stay close to the lifts - no need of a 4wd Snow tires are mandatory.
how long driving verses a 2 hour shuttle from Vancouver airport?
Seattle airport is south of Seattle -if you have to cross Seattle at rush time it can be ugly.
With no traffic you can get to the border line-up in about 2 hours. Coming into Canada is usually not a long wait - But weekends can see line-ups of 2 hours to cross as Canadians return and American head north. From there (I live just north of the border) I can drive to Whister in 1:45 on a good dry day but I know the road well, leave to avoid traffic, have a radar detector and a lead foot.
Vancouver which you have to pass also has congestion which you to contend with and it is just as bad as Seattle)
Extremely over optimistic would be 4 hours but I would allow at least 6 if you time it well, and up to 8 if you don't. On the return trip to the USA increase same by another hour - US customs is much slower.
You can buy individual discount tickets at 7-11 in Squamish but you might get the same rate or better if you do a hotel package. There are prices in all ranges and budgets.
personal recommendation is: fly Vancouver, shuttle to hotel within walking distance of one of the
lift bases skip the car.
PS for skiing best base is Creekside (but has much less action than Village)