I have an HP printer. I do not refill the cartridges. I was told years ago that doing it yourself is a messy job and that ink goes all over the place.
I learned the hard way not to buy my ink at Walmart. The cartridges don't last very long if I buy them at my local WM. I buy them at Staples, etc. I order them by phone and I get free shipping which means that I buy several at a time. This works for me because it saves wear and tear on my car plus it saves on gas. I live over 25 miles from Office Max, Office Depot, or Staples.
What's frugal for me might not be frugal for another person.
It is entirely possioble that when I get a new printer it won't be by HP and that it will not be as expensive to operate. I've had this printer since 2003.