Regarding the Potion specialist who wants to settle down:
There are rules in D&D 3.* for earning experience outside of combat. Any professionally challenging situation can qualify, and unless I'm mistaken the standard Exp for "Role Playing adventures" (i.e. handled through RP, not conflict) is 50 x Character Level.
How else would non-adventurer types ever advance a level?
Consider this aspect: A crafter who doesn't face this limiting factor could craft 1,000 gp in goods a day (at a 50% profit margin), and rather quickly be the richest man/woman in town.
In my game worlds, when PCs visit a city and want items custom made, the crafter will probably have to delay their order. The local gentry/nobility have potions, arms and armor etc. on backorder, and the needs of the city/kingdom come ahead of strangers, even if the strangers have lots of gold.
You want instant gratification? Talk to the local lord and explain/justify your need. If he agrees, you can jump the line.
Oh, what's that? He'll agree if you just do a little job for him? Sounds like a good DM tool/plot hook.
And no matter what, there is a maximum Exp per month that crafter can spend on items. His batteries are always on the low side. Some of the Exp he spends on items he has to earn by going out and finding the rare and exotic materials used in the crafting. (Why yes, that exorbitant GP cost for crafting has to go somewhere, it isn't just a matter of pouring blood/life-force and gold into a bottle and shaking well.)
So this also helps provide the DM with adventure opportunities: "Yes, I can craft a Dragon Slaying blade for you. Bit the grip must be wrapped in the raspy skin of a Fiendish Shark, as an anchor for the dark energies needed in such a weapon. So if you could get me some of that, I could help you..."
These rules were created to limit PC item creation, yes, but the greater limitation is the down time they have to spend on it. Taking the rules into account in your game world over all helps give that aspect of life a bit of texture, and makes the game world a bit more "real".