Did you ever notice that your eye drop bottle is refillable? What I mean is, the piece in the top is removeable, and you can fill it up yourself. I suppose you could use it for anything that you wanted to measure by the drop.
I buy the cheapest eye drops I can find, open it up and dump all the contents down the sink. Then fill it up with salty water. When my eyes are feeling dry, I squirt some in. It's also helpful in the morning for rinsing out any gunky stuff.
I'm not sure soft lens wearers could do this. And if you have an eye condition, you should use whatever your doctor suggests. But for everyday dryness this works pretty well.