Josh,
Sorry, I did not read this carefully enough. You have the right idea to make a child table for Category, Description, Price. The Category field in the child table would be a drop down list.
In the Parent Estimate table's form, embed the child Category record. You do this by embedding the report link of Estimate, then, in the properties for the Parent Estimate form, go to this report link. Configure on the right hand side to "display related Category directly on the form".
Table structure:
Estimates Parent >>> Child Category, Description, Price table.
Does this make sense?
