Hello Joshua Grossman,
Could you provide information about the growth rate field? It's not used in any of the example calcs or in the attaced excel spreadsheet example. Creating the first column is straight forward but the additional columns are confusing (at least for me).
Your question is another one of an "easy-when-in-Excel" kind.
Though it could be a "piece-of-cake-when-in-Tableau" as well.
For every matrix calculation one should have a matrix table --
it could be as simple as 2 x 2 for Tableau to start with.
Such a datasource table is called "Scaffold" --
following Joe Mako who pioneered the approach.
Using this datasource and a set of parameters (for CPM and Growth)
one could build dimensions via Tableau automatic Bins,
place them on a view in opposite and trigger domain completion
on both bins by setting Show Missing Values to ON.
Then one could use table calculations to fill the matrix.
Please find the attached.
Hope it could help.
PS your original datasource is just a diagonal of a matrix,
so it is not in the right shape for Tableau.