Trekker is correct and very fair in his post, in addition the laws of supply and demand will be an automatic check on how things develop.
With the cost of items (charged) being higher any guild with the Charming skill is encouraged to use their own skills rather than a charged item.
Vylar intimated that many herbs do the same job as potions, this stimulates the herb picking selling economy asnd gives it back it's importance.
What this structure does do is still retain the availability of goods to all but instills a system that means you can not have ALL potions/runes/items you WOYULD LIKE in limitless cheap easy supply.
Although there is a firm structure to be adhered to, as Kuurus replied to Foreigner a barter or trade off can occur occasionally - talk to a Loremaster.
To Cuchulain, I am sorry you were not around, please talk to Kuurus, Gandalf, Ramis or myself who have been spokeman for our guilds - I am sure you will feel happier after doing so.