Use the TTC website to find the deals and run around to the traders until you find one. The addon for TTC just shows the prices in game on the item card. And the software client just uploads price data as you find it. The software client is more useful if you’re a seller and have an actual account on TTC for your listings. Not required though. But for me, it’s advertising. This process works best for when you are looking for a specific rare thing for sale. Don’t bother with it for high volume items. They will be gone by the time you get to the store.

Be sure to set your awesome guild store filters as strictly as possible to minimize noise. Then start searching for what you need at all the guild traders. You won’t always get the best price. But as long as the price is within the range that the TTC addon suggests, you’re getting a decent deal.

Don’t confuse the difference between master merchant and TTC. They are vastly different in the data they provide and how it’s collected. Without getting into a big detailed post, consider that master merchant is only most useful if you’re in three to five large high volume trade guilds with a public trader in high traffic areas. And then you need to be collecting sales data for at least a week or two before the data is useful. Before you have that, rely on TTC price info.

Also for master merchant, set the option to exclude outlier sales. The ones that were excessively above or below the time-weighted average.

Focus on TTC for now and save master merchant for when you are actually selling competitively and have access to the sales data to make it useful. It’s also good for other addons that hook into the data (writworthy comes to mind, but there are many others). Again, only useful with membership in guilds that do a lot of sales. Because it pulls data from guild sales history you get access to when you join the guild. Versus TTC which is crowd sourced price listing data fed by people browsing stores and listing their items.