Editor: Quote redacted

Would be nice if you would provide all the information needed to answer your request for for help.  For instance, nothing you have posted even shows how this table, #TempCommonMatchFormatted, is...

Having grown up watching "All in the Family," no, you aren't.

Part of your problem is the multiple subqueries in your SELECT column list.  Each of those are a separately run query.
I am also assuming that the 1787 number of rows...

So, tell us again what problem we are trying to solve?

Try adding the following index when running my query:

create index [ix_SalesInvoice_SalesComparison]
on [dbo].[SalesInvoice] ([ShipDate])
include
(
  [BCustNo]
, [SalesAmount]
, [AVGCst]

Why are you posting new threads when you have already asked this question and been given an answer in another post.  You aren't helping yourself doing this.

Here is...