Exclusively for Prime members, Amazon offers the Systane Ultra Lubricant 0.33-oz. Eye Drops 2-Pack for $10.53. Add it to your cart via Subscribe & Save to drop the price to $10. With free shipping, that's at least $10 less than you'd spend for a 3-pack at a local warehouse store.
Be sure to cancel your subscription once your order ships to avoid being billed for subsequent purchases.