SUM for sales when there are multiple prices

We have a few places that we receive pricing for a product, so to account for it in our sales beastmode I have been using the below formula but it sometimes provides numbers much greater than the equation should provide.  An example would be a quantity of one * a price of 32 has (incredibly infrequently) given a price hundreds of times larger.

The beastmode is written in order of importance, and if the unit_price exists we would want to ignore the other options, but if it doesnt exist I want it to check for alternative_unit_price, etc.

Am I missing something?  Is there a better way to write the beastmode, or a more elegant solution?  Any feedback appreciated!

SUM(((CASE when `unit_price`>0 then `unit_price`
when `alternative_unit_price`>0 then `alternative_unit_price`
when `backup_unit_price`>0 then `backup_unit_price`
else 0 end)
*`unit_quantity`)
+
((CASE when `case_price`>0 then `case_price`
when `alternative_case_price`>0 then `alternative_case_price`
when `backup_case_price`>0 then `backup_case_price`
else 0 end)
*`case_quantity`))