I love Urban Decay Primer Potion, too. I only use a tiny smidge each time, but it keeps even my cheap eyeshadow (I'm just starting to collect the better-quality stuff) where I put it and prevents creasing. My eyelids are typically very oily, too. Love the stuff!
I watched a video on YouTube of someone cutting open their "empty" primer potion bottle and was amazed at the amount still in there! I think this one bottle will last AGES with the tiny bit I use, if I can get all that extra out.
This sounds crazy, but my dad has a woodshop/machine shop workshop behind his house. I'm thinking I might take the bandsaw to the primer potion bottle when it's "empty". I should probably video that...