The higher setting, the more ink you use. For drafts, use the low setting. And while you're at it, recycle on the backside of previously used paper to save paper costs. Using a multi-colour cartridge can add to the cost. If one colour is exhausted before the others, the entire cartridge has to be replaced.
All inks saturate the paper, some more or less than others.
Lighter paper will tend to use more ink than heavier paper. Condition and cleanliness of the machine. Generally, faster printing, more capacity, and the ability to support larger sized print stock, 11x17 plus. Some colour printers will have built-in photo technology, while others use single cartridges for each colour. The amount of maintenance your printer will require depends on several factors.