avgBuy (Avg Buy Price)
From the TSM Accounting module, avgBuy and avgSell are the average prices that you purchase and sell a particular item. If you have 'smart averages' enabled in your Accounting options, your average purchase price (avgBuy) will be the average of your most recent purchases i.e the items in your inventory.
minBuy and maxBuy are the minimum and maximum price you've purchased an item for in your Accounting data. Conversely, minSell and maxSell are the minimum and maximum price you've sold an item for in your Accounting data.
Crafting (Crafting Cost)
From the TSM Crafting module, the Crafting cost of an item is the sum of the material prices (matPrice) of each individual item used to craft the recipe. You can change how matPrice is calculated by default in your Crafting options under 'Default Price Settings', you can also change the individual matPrice for items in the Materials tab of your Crafting page. An item can only have a matPrice if you have a recipe that uses the item as a material.
Destroy (Destroy Value) vendorBuy (Buy from Vendor) vendorSell (Sell to Vendor)
A particular items Destroy value is the value of the items you would receive by destroying it, on average. Destroying an item can be done by milling, prospecting or disenchanting it. By default, the Destroy value is calculated with the DBMarket values of the items you would receive, you can change this in your Tooltip Options.
vendorSell is the value of a particular item when you sell it to a vendor. vendorBuy is the cost of a particular item you can purchase from a vendor. Note that vendorBuy is only populated for a particular item when you visit a vendor that can sell it.
DBMinBuyout (AuctionDB - Minimum Buyout)
DBMinBuyout is the lowest priced auction on your realms Auction House, as of the last pricing update processed from Blizzard's Auction House API. This value is not 'real-time', your pricing data may be 30 minutes or older before the next pricing update. If an auction is posted between pricing updates, this value does not get updated with the new lowest priced auction until the next pricing update. If there are no auctions for a particular item on your realms Auction House, DBMinBuyout could be an invalid price source.
DBMarket is a weighted 14-day average of the auctions listed for a particular item on your realms Auction House, favoring the most recent 3 days of pricing data. It is explained in much more detail on the AuctionDB Market Value page. Note this value does not indicate what an item will sell for, only what the item is currently being listed for on your realms Auction House.
DBHistorical is a 60 day average of the DBMarket value for a particular item on your realms Auction House.
DBRegionMinBuyoutAvg (AuctionDB - Region Minimum Buyout Average)
DBRegionMinBuyoutAvg is the average of DBMinBuyout across all the realms in your region for a particular item, as of the last pricing update processed from Blizzard's Auction House API.
DBRegionMarketAvg is the average of DBMarket across all the realms in your region for a particular item.
DBRegionHistorical is a 60 day average of DBRegionMarketAvg for a particular item in your region.
DBRegionSaleAvg is the average sale and purchase price for a particular item in your region. This data is collected from TSM Accounting data via the TSM Desktop Application.