mucat is correct. If you try to pay a fellow wizard for his spells, the base table for cost of spell services is not sufficient. He would want to send you on a quest for a rare herb or ask for alot more from you to give up on of his hard earned spells. If you happen to find a scroll of X in the local market, you could buy it and then make all the appropiate rolls to incorperate it into your spell book.