FYI on the Costco rate: that is still an unlocked leisure rate, and it's still subject to market pricing. While it probably is the best of the available leisure rates right now, travelers who have access to a company code as an employee of that company are likely to do better using that at this time, because corporate rates are customarily locked in for the duration of the company's contract with the agency, and usually are not subject to market price fluctuations.
If you work for a company that has employees who normally travel for business (even if you were never one of those employees), ask whomever handles travel accounts at work if there is a rental care code available (if you don't have a travel rep, someone in accounts payable is likely to know). Most of the time companies do not care if employees use the negotiated codes for leisure travel on their own dime.