The lore of magical potions goes back to the earliest stories. Ingesting the right combination of substances must do something, right? It certainly does in fantasy settings, if not in the real world. From witch doctors and priests to warlocks and wizards, it seems like everyone has a special recipe to cure this or that. In literature and in reality, people ingest potions for all manner of things; finding love, increasing fertility, luck, beauty, strength, curing all manner of ills, and other such miracles.
The above potion generator assumes that anyone investing the time and resources into a potion would do so only for useful purposes. To that end, there are no bizarre effects like inflicting lycanthropy or changing one's gender. The worst that can happen is that the potion has spoiled or was made wrong and has become toxic.
You might also notice that a detailed description is given for the vessel containing the magic potion. Like fine wine, the container belies the contents, or so the seller would have you think. If you are going to spend a few years income on a potion, you want one that does not come in a pig's bladder. Also, by describing the potion, my hope is to give the players more appreciation for the rarity of these things. And it is also nice to have a fancy bottle left over after your potion has all been imbibed.