I built a calculator that prices magic items based on how much they actually disrupt your game, which I think is especially useful for homebrew items where you can't just look up a price.
The core idea is a 9-level "disruption scale" where you evaluate what the item does at your table. A +1 weapon is a meaningful advantage (1,000 gp). A Decanter of Endless Water in a desert survival campaign is an economy breaker (80,000 gp). Same Decanter in a city campaign? Minor convenience (300 gp). The scale accounts for context in a way that's hard to capture in a fixed price list.
It also factors in item type, market conditions (auction houses, fey markets, infernal emporiums), modifiers like attunement and curses, and haggle results.
A couple of design choices worth calling out since they've come up in earlier feedback:
I know attunement items tend to be more powerful, but that power should be reflected in where you set the disruption slider, not in the attunement checkbox. Attunement itself is a cost to the buyer: it uses one of three slots. A +1 sword that doesn't require attunement is more flexible than one that does, so the non-attunement version should cost more, all else being equal. The disruption slider is where you account for the item's actual power level.
A major city charges more because there are more wealthy buyers competing for items, guild regulation, and prestige pricing. A black market discount reflects the risk and dubious provenance, not a larger supply of magic items.
Would love feedback from fellow homebrewers. Does the disruption scale make sense? Are there items you've made that price weirdly with this? Anything feel off?
Here's the tool: https://cros.land/magic-item-price-calculator-for-dd-5e/