The Costco sourced Canon refills we used, and were pleased with, were ordered online from Costco.com. I've heard the Costco in store refills are not as good but I have no experience with them.
With respect to Kirkland brand, at one stage of my career I worked for a consumer products megacorp selling to Costco. Some of the private label (i.e. Kirkland brand) products were identical to the national brand merchandised. These products were labeled "Kirkland" instead of the national brand in the production lines and shipped in Kirkland packaging. Other products were made to the national brand spec but modified for Costco/Kirkland to differentiate the offering from other stores. For example the Kirkland item might be a different color from the national brand or include a bonus accessory items inside the package. Finally, there were products made to Costco's specifications which differed from the national brand products. The Costco specifications were in some instances designed to deliver higher quality. In other instances the specification might be for lower quality ingredients or parts to hit a specific value price point. I might add, Costco also sourced some Kirkland brand products directly from factories without going through a national brand manufacturer.
While Kirkland brand products are generally high quality, and equal to or better than the national brand products, each product has its own specifications so the purchaser does need to examine or test each product to determine its utility.
We live in a period where the government's CPI is under reporting inflation. Raw material prices are increasing faster than the 2% inflation rate. Both retailers and manufacturers are responding by substituting raw materials, changing specifications, moving production to new factories and often new countries (i.e. shifting from China to Vietnam or Cambodia), changing package size (a 16 ounce can becomes a 14 ounce can), etc. All of these actions are being taken in an attempt to delay raising price per unit or package as long as possible. Unfortunately most of these actions have a negative impact on product quality.
The founder of Costco retired over a year ago. He was a hands on executive, highly involved in running the company at every level (store operations, product, etc). He was relentless about maintaining Costco standards. Since his departure, as a customer I've noticed subtle changes in both store operations and product quality. It may be his successors, faced with a margin squeeze with rising prices, are beginning to behave like traditional retailers and manufacturers -- cutting costs by reducing headcount and product quality. If so we consumers can expect to experience a decline in the customer and product experience that differentiated Costco from other retailers and allowed it to grow a strong consumer franchise. The longer checkout lines, dirtier floors in the store, and occasional stock outs I'm seeing in my local store are not a good sign. The decline in quality of the toilet paper is also a bad indicator.
Unfortunately businesses tend to change for the worse when visionary founders depart the company. Wal-Mart after Sam Walton's death lost its consumer intimacy as his successors rolled out monster stores and expanded internationally. Apple seems to be struggling with product vision and store operations post Steve Jobs. Starbucks struggled with the founder left until he was brought back to run the company again. Costco may be beginning to lose its way as professional management by the numbers and committee replaces a visionary founder who had a unique instinctive insight into the mind and behavior of the customer.