I also did it. My calculations, unfortunately, are different.
Epson C88+ is under $100, pigment inks are next to nothing and 8.5x11 100 sheets of archival paper is around $50. 100 sheets of 8x10 FB are $100+.
If I have to buy same printer every five years it is $20 per year. So, basically we are comparing Letter sized prints for fifty cents per print, with one dollar 8x10 print. And running water from the tap isn't cheap where I'm.
Larger than 8x10, I just can't afford it as darkroom paper on FB. With current pricing for FB paper people like me are priced out from darkroom and pushed to ink printers. Plastic RC... I'd rather print it from printer on real paper. Actually, something happened and I just can't print on RC anymore. Many of my RC prints are turning grey within few months. It could be same everything. Paper, chemicals. One day prints are fine, week later same everything, prints are turning grey. While FB is not a problem, same chemicals, water, place, enlarger and me