Your best bet with the newer HP models that support it, is to go with the Instant Ink subscription - That way you're covered on ink as long as you're a subscriber and you're going to get your value out of the cartridges even if you don't print a lot.
The current (estimated) price of the #67 cartridges are as follows - These are for standard capacity, not XL, and not XXL like you get with Instant Ink:
Black: $16
Tri-color: $17
Total, that's $33 per set. If you subscribe to Instant Ink, which is only $2.99 for 1 month and 50 printed pages, you're only going to spend $36/year. With this program, if your ink dries out from non-use, they send you fresh cartridges. You're literally guaranteeing yourself at-the-ready ink for your printer for just a few dollars more than ONE set of cartridges cost. Plus, the cartridges they send you are EXTRA HIGH CAPACITY so you're going to get a lot of printing out of each set. It really is a tremendous value.