Purchasing a magic item requires time and money to seek out and contact people willing to sell items. Even then, there is no guarantee a seller will have the items a character desires.
Finding magic items to purchase requires at least one workweek of effort and 100 gp in expenses. Spending more time and money increases your chance of finding a high-quality item.
A character seeking to buy a magic item makes a Charisma (Persuasion) check to determine the quality of the seller found. The character gains a +1 bonus on the check for every workweek beyond the first that is spent seeking a seller and a +1 bonus for every additional 100 gp spent on the search, up to a maximum bonus of +10. The monetary cost includes a wealthy lifestyle, for a buyer must impress potential business partners.
As shown on the Buying Magic Items table, the total of the check dictates which table in the Dungeon Master’s Guide to roll on to determine which items are on the market. Or you can roll for items from any table associated with a lower total on the Buying Magic Items table. As a further option to reflect the availability of items in your campaign, you can apply a −10 penalty for low magic campaigns or a +10 bonus for high magic campaigns. Furthermore, you can double magic item costs in low magic campaigns.
Using the Magic Item Price table, you then assign prices to the available items, based on their rarity. Halve the price of any consumable item, such as a potion or a scroll, when using the table to determine an asking price.
You have final say in determining which items are for sale and their final price, no matter what the tables say.
If the characters seek a specific magic item, first decide if it’s an item you want to allow in your game. If so, include the desired item among the items for sale on a check total of 10 or higher if the item is common, 15 or higher if it is uncommon, 20 or higher if it is rare, 25 or higher if it is very rare, and 30 or higher if it is legendary.
The magic item trade is fraught with peril. The large sums of money involved and the power offered by magic items attract thieves, con artists, and other villains. If you want to make things more interesting for the characters, roll on the Magic Item Purchase Complications table or invent your own complication.