Something has been bothering me about the Robe of Useful Items. I've kept glancing over it and getting the feeling that the items it held were worth way more than the item itself cost.

Yesterday I was finally bored enough to actually run the numbers. It's a pretty substantial difference.

Because of the randomness involved, I did the calculation for the expected monetary contribution of each patch based on it's value, probability of being rolled and any potential reduction in selling price due to selling. I assumed at 50% reduction for non-magical, non-treasure items.

Here's the summary, I'll link to my code and the full breakdown at the end:

Expected Cost: 350g

Value of Fixed Items (Patches that will always be there): 36.12g, or more reasonably 18.06g after losses from selling

Expected Patch Value (Raw): 166g

Expected Patch Value (With Losses From Selling): 159.7g

Expected Patch Value (Treasure Only): 123g

Average result of 4d4 patches -> 10

Meaning the average Robe of Useful Items will carry 1230g worth of just treasure. If you sell the mundane items at 1/2 price and the magical items at full price, you get an expected value of 1615g

Profit (Treasure Only): 880g

Profit (Selling Everything): 1265.08g

Additionally, each robe has a number of patches that were difficult to define a precise value too. These are the "Iron Door", "Window", and "Pit", because they don't really have analogs anywhere else in the system. For the purpose of my calculations I referred to them as "Intangible" in my code, because of the difficulty of assigning a value to them. The average robe will have 2.1 of these patches.

Final Verdict The Robe of Useful Items is fucking amazing and worth way more than its asking price. Players: Please use this knowledge responsibly. DMs: If your players start abusing this, then the only Robes that are available will have already been stripped of their treasure and magic patches. Or you could just give them a Robe of Only Ladders

Here is my code and full results. I used Jupter Notebook with Python 3.6 to write it. Refreshing the page should show the output.