Like Darren, I have moved to only black prints. I didn't use the color in the shop enough before it dried out or went bad, what ever happened to it. For prints, Cheryl uses CVS. If you do enough, you start getting coupons and they get really cheap.
One thing I did once, was hit the sales. Black Friday was the bomb. I could buy several printers, same models, cheaper than refills. When I needed ink, I just opened a new printer right out of the box and tossed the printer. Not very enviro friendly, but sure helped the wallet.
If you don't take pride in your work, life get's pretty boring.
Rule of thumb is if you don’t know what tool to buy next, then you probably don’t need it yet.