Before anyone says "why doesn't it support X": I made this for my personal use and I use MM and decided to release it. This addon will take the MM value of the items in the active toon's worn equipment, inventory, bank, craftbag and guild listings and try to give you a net wealth.
The main command is /wealth. There is also /wornsum (equipped), /bagsum (inventory), /banksum, /craftsum (Craft Bag). I think they are somewhat self-explanatory.
/stolensum is a special case: it is automatically called when a guard is trying to arrest you and it gives both the MM value of your items and the vendor value, since many stolen items cannot be traded. It only applies to what is worn/carried as they are the only items at risk. The other commands already sum stolen tradable items in the normal sum, while this is more specifically for knowing risk.
These were more so for debugging, but I thought the bank one was cool so I left them. These commands will give you a data dump (list) of the items in their respective commands:
Craftbag doesn't have a dump because of several reasons that I'm too lazy to list.
All, Bound or Unbound
Wealth, Worn, Bag and Bank have three variants of the command. The "all" command is simply the default one. If you want bound only you add "b" if you want unbound only you add "ub" For example, the worn command is "/wornsum" if you want unbound only, use "/wornsumub" Craftbag doesn't have a bound/unbound option because I don't think there's anything bound that goes in there that would have value. If I'm wrong, correct me and I'll add it.
Guild listings must be viewed before the game allows you to be aware of them. All this means is that if you want your guild listings included in the wealth evaluation, simply view each of your listing pages (the items must appear; if the listing is blank because it didn't load, it won't work) before using the wealth command. This uses the value you listed the item at rather than the MM value because what you have listed it for is more relevant to you.
This may seem confusing for some people because it looks more complicated than it is, so feel free to ask. If you just forgot a command, you can always use /wehelp for a refresher.
Thanks to @zopo25 for testing.
Version 1.05 - uses vendor value for items without MM.
Version 1.04 - API bump.
Version 1.03 - added risked stolen items sum.
Version 1.02 - craft bag fix.
Version 1.01 - added unknown listings on individual checks.