In Tom's view, efficacy is all about producing the highest number of cars with the lowest amount of money and in the lowest amount time time possible.

[alpacinou]

Is this correct and natural?

In Tom's view, efficacy is all about producing the highest number of cars with the lowest amount of money and in the lowest amount time time possible

 

[Barque]

In Tom's view, efficacy is all about producing the highest number of cars with the lowest amount of money and in the lowest amount time time possible

It's ungrammatical (though I daresay you may have just made a typo). Also, "lowest" is the wrong word for what I think you mean as regards time.

It's also unclear. Efficacy is a general concept and not limited to car manufacturing.

 

[jutfrank]

I don't think 'efficacy' is the right word for what Tom has in mind.

at the lowest cost
in the shortest time possible

 

[Barque]

"Efficiency" is possibly a better choice.

But even then there are other problems with the sentence. You can produce a large number of cars at very low cost in a very short time, but if they all continuously break down and guzzle fuel, you aren't really being efficient.

I do get what the OP wants to say but it isn't something that can be condensed in a single sentence in my opinion.