How to summarize logicals in IF condition?

Hey guys, I am breaking my head for something very simple.  

I'm calculating the total margin in a Cars table.  In a simple context, things would look like this, 

CarsMargin_ideal = CALCULATE( 1 - SUM([purchase_price])/SUM(selling_price), 
    FILTER( Cars, [was_sold] == 1) )

The problem is some entries don't have prices, which in most cases don't matter because they won't be added.  
But in special filters, those are all the cars so it looks as though the margin is 100%.  

The way I'd want to fix this is: 

CarsMargin_ideal = CALCULATE( IF( AND( SUM([was_sold]>0), NOT(ALL(ISBLANK([selling_price]))) ),
        1 - SUM([purchase_price])/SUM([selling_price]), BLANK( )), 
    FILTER( Cars, [was_sold] == 1) )

One would notice that the function ALL doesn't refer to a logical ALL, but something else.  And everywhere I look I cannot find a way to compare all entries in what results a logical vector.  

Simplifying the question, how do I go about the condition in this piece of logic:  

CALCULATE( IF( any_or_all( logical_vector ),
    calculation, blank), filters )

Thanks,