Q219 - What are some good feats that reduce the cost of buying items / Increase overall wealth or capability to produce wealth and good feats for increasing profits by selling higher or whatever else there might be.
Mercantile Background is in one of the FR books (PGtF, I think). It lets you sell at 75% market rather than 50%, and once a month it lets you but at 75%.
When used for item creation, Craft (Poisonmaking) advances in gp rather than sp, meaning it can create ten times the value of items in the same time frame, and if you have a reliable source of ingredients, it only costs 1/6 market to get the ingredients rather than 1/3.
Going cross-setting, Dedicated Wrights are a kind of homunculus from Eberron that can craft for you. Make some, give them masterwork poisonmaking tools, and set them to work making whatever poison you can manage to secure both an ingredient source and a buyer for. They should pay for themselves within a year, after which it's pure profit. If you're feeling cheezy, use planar travel to speed up that first year.
If you have Mercantile Background, and lower your production costs enough, you can reliably turn a profit. If you're an Artificer with Extraordinary Artisan and Legendary Artisan (-25% gp and XP costs for all crafting), you can stack Magical Artisan from FR (-25% XP and GP costs for a single item creation feat, we'll say Craft Wondrous Item) and Apprentice: Craftsman (DMG2, -10% GP costs for all crafting), then when you make something, it costs you 25.3125% market in GP and 2.25% market in XP.
So, if you were to make, say, gauntlets of Ogre's Strength (4000g), it'd run you 1012.5 gold and 90XP. You can buy magic items and then salvage them with Retain Essence to get the XP you need, using your monthly discount and running you 1687.5g, for a total of... 2700g. And you sell it for 3000g.
Gee, that's not much of a profit. 7.5% of market value, once a month... I thought it would be better, though I suppose if you made something considerably bigger, you'd turn a much larger profit. 7.5%, still, of course, but 7.5% of a much greater base.