No need to be confused. "Darn pretty good" falls short of "cheapest always". Even autoslash is not "cheapest always". There are (nearly "always") multiple ways to skin a rental - so the only correct conclusion would be costcotravel.com is NEVER the cheapest way to book (because Costco - for its profit, anti-consumer reasons - doesn't deal with Cashback sites). This being said, there is no harm to start your research with Costcotravel's page to get a quick idea of where you should go next.

I repeat for slowly-comprehending, because this mistake will still be made by million readers: NEVER EVER book at costcotravel.com EVER!! Until Costco hooks up with Cashback sites, you'd be part of a problem and not of a solution to "cheapest rental"