you can search the internet for the labor cost of tile installation for your area. I'd specify Mable or porcelain since I'm accustomed to paying slightly more for stone tile.

$15 / Sq ft would be very expensive in Los Angeles. I have no idea what the rate would be in Toronto.

I think it's over priced too. Get more bids. Maybe if you scraped the old tile off you can save some bucks?

definitely overpriced, even for Toronto

Natural stone had more restrictive setting requirements than does ceramic or porcelain. A three day process for more difficult tile with more expensive setting materials from a fully licensed and insured tile mechanic would be between $3000-$6000. Depending on if this was a 12x12 laundry room floor or a properly constructed and waterproof herringbone tiled shower.

You don't get to judge a per square foot price on tile without also judging the entire job as a whole, and the TIME and difficulty associated with the job. Most tile contractors will give you the price for the complete job, not a square foot price. A square foot price is almost meaningless when it comes to the less straightforward tile jobs.

15/sf might be a lot for installation, but removal of existing tile is a drag, and then the floor needs to be prepped for installation (meaning no bits of thinset left from the first time), and if it's for all of that, it doesn't sound so out of control. still, you lose nothing by getting additional bids.