One of my essential add-ons for playing the economy is
Master Merchant. It's a fantastic addition, but sometimes it takes a bit of poking to understand some of the functions. I get whispers pretty frequently from people asking about how to use a feature, so I figured I would just pull together some of the most common asks. To be fair, most of these points are already made on the Master Merchant description page at esoui.com. But I wanted to provide a little more verbose description for those new to the markets.
History Window
After you install Master Merchant you'll have a new window that appears when you open the Guild Store at a banker or while accessing your mail. It provides sales history across the different guilds you belong to. This is the sales history window highlighted in the screenshot below:

The way the Guild Store/Trader system works in ESO is different than the auction house system available in many other MMOS. A full description of how guild stores and traders work is too long for right now, maybe it's something I'll cover in another post. But the simplest summary is that each guild is effectively a marketplace on its own. So if I'm a member of two trade focused guilds, and you're a member of two different trade focused guilds, we might potentially see very different common prices for sales and amount of demand. In ESO the focus is a little less on overall price for an item, and more about what the price is for the guilds you have access to.
Fortunately you have some great info available to help you determine that price. You have access to the sales information for all the transactions that take place for any of the guilds you're a member of. And that's what's presented in the Master Merchant history window. There are controls available to filter the info to just your sales or show them across all sellers, controls to roll up sales by seller or display each item individually, and a search box you can use to narrow things down. The history window is a great way to get a feel for what items are moving in the most volume or at the best prices across your guilds. For instance, this is how I view my sales for the day so far in Master Merchant, a view with just my sales and a single total line per guild:
Item Tooltips
Having access to the history across your guilds is great info, but a vast majority of the time you just want to know what the common price for an item is. For instance your bags are full and you really want to loot the nirncrux that just popped up unexpectedly at a node. What can you destroy in your bags that isn't going to leave you crying later? Master Merchant adds two items to the tooltips that pop up when you hover over items in a list or click on their link in chat:

The extra info added by Master Merchant is highlighted with a light blue rectangle in the image above. The first part is the line "MM price (153 sales/1530 items, 31 days): 236.60". Broken down into fields:
- 153 sales : Master Merchant knows about 153 listings that were successfully sold across all my guilds.
- 1530 items : You can sell more than one item in a stack. In my case the 153 listings had a total of 1530 items, which is an average of 10 items per listing.
- 31 days : The amount of history used to calculate item info, by default all info. You can assign different ranges to the shift and control keys, and the tooltip will update if you hold down shift or control while the tip is visible.
- 236.60 : This is the average price per individual item across all sales. So a single Columbine sells for just over 236 gold on average for my guilds.
The second bit of additional info that Master Merchant adds is the chart just below the "MM price" line. That's a scatter plot of the sales Master Merchant knows about for this item with the price on the vertical axis and time on the horizontal (older sales on the left, newer sales on the right). The dots on that graph are color coded by guild, but only if you have different colors set for your guilds. Guild colors are set in the social settings menu. Master Merchant uses the same colors for guilds as the chat box. The appropriate settings are highlighted with a light blue box in the screenshot below:

That scatter plot can be extremely useful to see trends in the data. Maybe certain items sell for a much higher price in one guild, you can tell from the color of the dots. Or maybe the price of a newly introduced item is trending down now that it's becoming more popular, you can tell from the dots trending down in the graph. Offload that item before the market tanks! I'm looking at you Perfect Roe.
Pricechecks
Chances are you've already seen something like "Pricecheck [Sanded Maple]" or just "PC [Sanded Maple]" in zone chat or in your guild chat if you're a member of a larger guild. That's someone asking for what other people see as the price for an item. Because the marketplaces in ESO are based around guild stores and traders different people will see different average values. So if someone is in a guild that's only shown a few sales for an item, or if they aren't in a guild at all, they'll often ask in chat for item info. Fortunately Master Merchant makes it very easy to post the summary line from the tooltip into chat to respond to these requests. If you right click on an item link in chat you'll get a popup menu that has a "Stats to Chat" option:
Deal Quality
The other place where average price info is most useful is when buying items yourself from a guild store or trader. Sure, you could roll over each item and check the sale price against the average price according to Master Merchant, but that can be really cumbersome. So when you view a list of items Master Merchant will put a summary deal quality value right in the list for you, with a numeric value color-coded based on the price of the sale relative to the average:

Negative values are above the average Master Merchant price by the percent listed, and positive values are under the average price by the percent. The color coding is there to make it easy to spot deals. The colors in order from worst deal to best deal are:
- Red - bad deal, item above average price
- White
- Green
- Blue
- Purple
- Gold - fantastic deal!
Keep in mind however that price isn't the only determinant of value for an item, it's also related to demand if you're planning to flip the item. So before hitting buy right away on those purple and gold items it might be worth checking your sales tooltip to see how many have sold.
Feedback or Questions
If there's anything I got wrong in this guide, or something I left out that's really important for getting the most out of Master Merchant, please let me know. Leave me a response here or contact me in game
@Revry. And if you have questions or would like to join our DC focused trading guild Tinkers'n'Traders please contact me. We're always looking for more folks interested in exploring the economy side of ESO. See you in game!