Mike, there's a simple answer and a more detailed one. Simple answer: Generally, your patron is going to be of somewhat limited assistance in buying and selling magic items. Without having the rules in front of me at the moment, if I recall correctly, criminal organization patrons have a "fence" perk that allow players to assign the sale of a magic item to an intermediary rather than expending the time in downtime activities themselves. Other patrons may have similar perks. I don't recall any of the patrons having a "buy magic items" perk, although I might allow some version of a perk that made contextual sense. Presently, the group has aligned themselves with House Kundarak. If someone was looking for an item that was associated with House Kundarak--a Keycharm from the Eberron items, for example, or some type of warding glyph or alarm--I'd definitely consider lowering the cost and time involved in buying the item. But if it's not a House Kundarak item, at the moment, I don't think that relationship would help. More detailed answer: in general, the rules for buying magic items in XGE and elsewhere are an imperfect compromise. My impression is that the 5th ed. rules for buying magic items are designed to make it possible, but difficult, to obtain specific items outside of an adventure. I think the game designers recognized several things: Magic items are essential elements to any D&D campaign Over time, experienced players and DMs learn which items are particularly useful to certain PCs (a Rod of the Pact Keeper for a warlock or Wand of the War Mage for a wizard, for example) Providing ready access to those items could spoil the special reward of finding magic items in adventures and could provide some PCs with powers and abilities that are imbalanced relative to the campaign's development It was difficult for the game designers to strike a defined balance regarding the availability of magic items and still provide DMs with control over the prevalence of magic in a particular campaign It's a terribly ill-defined game dynamic, but one that's been characteristic of D&D since the beginning. Reading the rules, one can see that the designers have tried over time to create hierarchies for the prevalence of magic in a given campaign, but ultimately retreat from making the rules hard and fast. I just received as a present a book called Art & Arcana, which is a history of D&D expressed through its evolving art; really interesting. Seeing all of the official campaign settings that have published over the years--Greyhawk, Forgotten Realms, Ravenloft, Dragonlance, Spelljammer, Dark Sun, just to name a few--it's understandable that the game designers threw up their hands when trying to make these rules uniform. In Eberron, the campaign setting designers went a bit further in making explicit that magic is readily available in the way technology run on electricity is in our world. High-level magic--above the level of "common," or that practiced by the low-level magic using magewrights--is still rare and powerful. So, longer and more involved answer: in the absence of any better way to regulate access to buying powerful magic items, meh, we've got the somewhat crummy rules-as-written, which are ... reasonable, I guess. <shrug>
