Query Across Several Columsn/Rows of Data

I have tables in a single sheet organized similar to this:

I want to write a query that can summarize the values of each line item uniquely. For example, total "Labour" across all 5 invoices. I can't seem to get a query to work across tables.

I have a query like so, that works for one instance of a table:

=QUERY(A4:B6, "select A, sum(B) group by A order by A") 

But I can't extrapolate this logic to extend across data like this.

Does anyone have insights into if a QUERY statement can fit this use case?