You NEED to set a Part Number

Note for your part to appear in the query command, it must have a part number (not just a name), otherwise it will not show.

Setting simple values in custom properties.

If you would like to add a static (simple) price to your parts that will appear in the query command and be calculated, it's very easy to do so. Simply go to the "Custom properties" area of your part, then add a new custom property with the name Price, and add a value of any number. This will then display that price in the query command, as long as you also have a Part Number set. You can do the same for other simple values, like "Supplier", "Color", "Description" and so on. For values that you would like to change, like length based pricing of steel sections, then see the entry below.

‍Setting dynamic text in custom properties or part numbers.

To set dynamic text in custom properties or part numbers, start by adding the = (equals) sign at the beginning of the field.
You can then type in Parameters, and also equations. For example the custom field could be called "Price" and look like this: =(PartHeight/1000)*15 This would be used to calculate a "Per Metre" price of $15. This price would update when the part size changed, assuming the parameters were set up correctly. Note your parameters (in this case PartHeight), need to be at the same level (Shape, Part, or Assembly) that you are adding the custom property to. If they are not, they will not work. If your parameter is at the wrong level, you can add a new parameter at the correct level, and then drive it via the expression field so it always equals the same as your other parameter.

You can also reference sizebox handles in the dynamic fields, which allows you to sometimes access information at a different level. For example, on a part, you can get the extrude height of the shape by typing =Shape\Sizebox\Height

If you're looking to have automatically updating text properties like this, it's a good idea to also watch a video on parameters if you're not already familiar with them.