What you're wanting to do is quite readily achieved. In fact, as is often true with Excel, there are several ways to get from point A to point Z. Which is most appropriate depends very much on a number of other aspects of the full situation.
My guess is that there are lots of types of "Things" as well as multiple "Sizes" and some Sizes would correspond to Screws but not to Spanners. Or whatever. So personally--as a layman who occasionally uses hardware but is by no means an expert--I'd start by entering "Bolt" and then have an adjoining column that has a drop-down menu with sizes that only pertain to Bolts. Same for "Nuts" and so on.
If in fact the total range of products and sizes (ALL possible combinations) is a very limited set, then you could create a single drop-down list. But my guess is that this is NOT the case.
Another crucial question: do you expect the fundamental database (including pricing) to be static, or will it change from month to month? Will new items be added, old ones deleted? Etc. The answer to this will also determine the best approach.
Once the part type and size are specified, it would be quite easy to use XLOOKUP--or one of the other functions that looks things up in a database--to retrieve the rest of the pricing data.
If the workbook you have is not proprietary, would it be possible to post a sample or a complete copy?
