Cheapest doesn't always mean 'best policy to buy' for the following reasons:
1) You might be using a comparison website that doesn't include 'the cheapest' policy. The widest selection of policies found online in Canada is offered by BestQuote Travel Insurance Agency. Here's a link to their 'super visa costs' page which offers a summary of super visa prices, as well as the quote request form to ask for free instant quote:
https://www.bestquotetravelinsurance.ca/super-visa-insurance-bestquote-rates
2) The lowest cost policy probably does not cover expenses that might arise because of a sudden illness that is related to a pre-existing medical condition. You can usually find that coverage (advisable unless you know 100% that the person coming to Canada has no pre-existing medical conditions), but it will cost a little more. If a person taking high blood pressure medication buys a 'no pre-existing medical conditions' policy - and then has a heart problem while in Canada the higher quality policy is well worth it.
3) You also need to factor in administration fees such as refund fees. One of the cheapest policies available comes with big 12% of remaining balance PLUS $25 refund fee. If you are coming for less than 4 months, this will erase any cost savings offered by that policy!!! Why? Let's imagine that the policy costs $1800 versus $2100 for a better higher quality policy (with only a $25 refund fee). If there are no claims on the policy and the person returns after 4 months, you would expect to get an 8 month refund. The cheap policy will give you back $1200 less refund fee of (12% x $1200)+25=$169 so $1031 total cost for 4 months? $769. The more 'expensive' policy? (that comes with better benefit levels including coverage for pre-existing medical conditions, but only a $25 fee)? Total refund will be $1400 less refund fee of $25 so $1375 total cost for 4 months? $725.
4) Don't be fooled by the 'monthly payment plan' option either. First off, it's probably 10-30% more expensive than a comparable policy that you have to pay for on an annual basis. But, it can end up being a lot more expensive than that. Why? It asks you to pay $50 (completely nonrefundable), plus two months premium (which is also non-refundable unless the person can provide a visa rejection letter). So you are guaranteed to lose $50. If travel plans change, you could lose two months premium as well. But the third way that most people lose additional money with this 'affordable' option (offered by 21st Century) is that early return refunds are calculated based on 'unused months' of insurance - all the other super visa insurance policies use a 'pro-rated on a daily basis' for refunds (way better).
Here's an example (keep in mind that the numbers are worse for the 21stC monthly plan the older you are). For someone in their late 50s the monthly payment plan option ($0 deductible) is based on an annual cost of $2012.06 so you have to pay $335.34 + $50 = $385.34. A different policy would be $1649.80 for similar coverage. So yes, it will save you the $1265 up front. But 'financing' is not cheap. If you stay for 165 days you will end up paying for six months (5 1/2 gets rounded up to 6). So in total you have paid $1056.02 for the 165 days. The 'more expensive' policy you have to pay all 365 days for? It gives you a 200 day refund ($904) and charges you $50 refund fee. total cost for the 165 days = $1649.80-$854=$795.80. So it costs a person in their late 50s $260.22 more over those 165 days to use the monthly option plan from 21stC!!! You would be much better off putting the entire amount on a credit card, even if you didn't pay off the balance and you had to pay 20% on the CC card. And it's even worse for people in their 60s and 70s with more expensive policies.
Looking through the super visa options is easy with a site like BestQuote, but it's even better to give them a call when you have questions.