The BestQuote website is a good starting point for a little research into insurance costs, as the referral above mentions: you can see the most recent version of their 'rates' page by visiting their site:
http://www.bestquotetravelinsurance.ca/super-visa-insurance-bestquote-ratesThey've got some general info on purchasing appropriate coverage (you can get an instant free quote from a wide range of companies on any of these pages):
http://www.bestquotetravelinsurance.ca/parent-and-grandparent-super-visa-health-insurance as well as links from this page straight to the proper government web pages concerning requirements.
And, info on coverage for 'illnesses related to pre-existing medical conditions' (no insurance comapny covers foreseeable expenses rlated to a pre-existing medical condition):
http://www.bestquotetravelinsurance.ca/visitors-to-canada-insurance-compare-pre-existing-medical-conditions-stable-period