The circular argument on price is kind of amazing, but just to keep it going...
http://www.thestar.com/news/gta/201...rt_express_bus_to_stop_service_this_fall.html
When I was travelling to the airport from downtown during my pre-affording-a-taxi days, I used to take the Airport Express, usually from the Royal York. Definitely not a fast ride as they'd stop at least at Harbour Castle for more passengers but it was the budget travel from downtown. I remember the price as $15 way back in the day -- apparently it had risen to... yup.. $27 when shut down in 2014. But because it was $27 by bus probably made it 'feel' more budgety than $19 by comfortable train with Balzac's coffee. Or something.
Seriously, though, as an out-of-town (albeit well versed in Toronto, natch) visitor, by far the best thing about the UP experience was how easy it was at Pearson. As easy as grabbing a taxi, pre-paid, fast, didn't have to go outside in November. Anyone staying at Le Germain, Delta, Royal York, One King, etc., etc. doesn't have to go outside -- even the Hilton or Sheration or Marriott Eaton Centre, although all those are a bit of a hike. Even the King Eddy is a short block from King station.
Try it -- you'll like it.