|Is this the same data you were previously considering how to store? A lot depends on how much data, how much the data changes, and in how many places you need the data.
Suppose this one form with the eight combo boxes is the only place where you will need this data. You had mentioned building some kind of calculator or estimator, so it could conceivably consist of just one form. If that's the case, you might consider just manually entering the data in the form designer. Each combo box lets you type in the choices in the list.
A step up from that would be to put the values in an array. Then use that array as the data source to a BindingSource. Then use that binding source as the data source to the first combo box. Repeat the process for the other seven combo boxes. You need one array, but you need a binding source for each combo box. This is because a binding source has only one current position, so if you use the same binding source for more than one combo box, setting one combo box will immediately set all the other combo boxes to the same selected item.
Here's a similar question with code.
c# - Populate a combobox with array information - Stack Overflow[^]