I bought a Canon Pro-10 (pigment) printer in the fall of 2016 to do my annual stack of 8x8 inch B&W prints that I bind into books as Christmas presents for family members. I kept meticulous track of ink usage over the course of making ~1,037 prints. Using only OEM cartridges (which EVERYbody sells for $14.95, BTW, except Canon throws in free paper with multi-cartridge orders while Amazon and the local camera store - but not B&H - charge sales tax, and nobody charges shipping) I worked out an OEM ink cost of $0.676 per print. (For some reason, B&W prints use ALL of the inks, with Red cartridges lasting the longest, Gray used at 6x the rate of Red, and the others ranging from 1.7x to 4.1x the rate of Red.)

I saved a bunch of the OEM cartridges, and for 2017 switched to refilling them with Precision Colors inks. Images printed with the same settings from Lightroom, and looked the same on the same Red River paper as I used in 2016. I did NOT keep meticulous track of ink usage for the Christmas 2017 prints, but consumption did not feel remarkably different from 2016. I calculated the cost to refill at $2.00/cartridge, and a cost/print of $0.090.

So for the ~1,195 prints I made for Christmas 2017 I saved $700 by using third party ink instead of OEM ink.

I have never had an ink clog in the Pro-10 with either of the inks over the several thousand prints made so far. But if I did, I *THINK* I could just remove and soak the head like I used to do with the Canon S9000 (dye) printer I had years ago, and if THAT didn't work I might be able to replace just the head. Worst case, I could scrap the printer and replace it for less than the amount I saved by using third party inks for just one printing season. So far there's no indication that the printer won't keep going for the 2018 season, and if that happens I expect my savings from refilling ink cartridges will double. (YMMV, of course. If I only made a few prints a year I would stick with OEM inks. But at some volume level it just makes sense to consider third party inks, unless you sell prints and can build the OEM ink cost fully into the selling price.)

From the Canon USA web site page for the Pro-10:

Professional Printing Performance for Large Archival Photos. As a photographer, you take care to capture the best images possible and you want those images to look as good as you remember when you print them. The PIXMA PRO-10 Wireless1 Professional Inkjet Printer makes that possible with features that ensure incredible output. A new 10-color LUCIA *pigment* ink system features three black inks for amazing monochrome . . .

The Pro-1 and Pro-10 are pigment ink printers. It's the Pro-100 that uses dye inks.

I would never buy ink from a company that didn't make its own product so Costco is not something I would even consider. I would suggest that even today the LD or Precision Colors inks are of a much higher quality than Costco refills. (BTW - one thing I always hated about HP black ink was its tendency to fade to brown or blue very quickly for text printing)

Just curious about 2 things -
1) You printed the exact same picture and hung them in the same place, leaving them up for over 6 years ? Was the purpose to do a long term comparison ?
2) If OEM is important, why did you not use an HP or name brand paper ?

My experience is that the papers are as important as the ink for longevity of prints. Knowing a little about your background I am not doubting your argument, just curious why you would not use higher quality paper for the testing and verify the manufacturing process was chlorine free. To my untrained eyes - the fading looks more like a reaction to the paper since every ink is reducing to the same color almost universally.

Edited:
*Although after looking closer at the prints, you can see where the colors appear unaffected under the tape used to hold the pictures up so paper would not be the cause*. Thanks for any insight.