Plus, many "potions" in my game aren't actually in bottles at all - you get enchanted fruits, biscuits, and many other small edible items; you get tokens and tags that need to be snapped to take effect; you get pouches of powders...
A mix of all sorts of different sizes and shapes, much like perfumes are available in a wide range of bottles in our world. (And that's even with the advantage of our modern methods of mass-production. I don't envisage D&D adventures, even those in Eberron, having the advantage of those techniques.)