Why use heat transfer plates?

Why use heat transfer plates?

Let's take the increased profit potential, of the longer install time for heat transfer plates, off the table.

I see that you can lower the water temp. by 40-50* due to the increased heat transfer efficiency.

But, can't you get the same results by installing 2 or 3 times as much PEX per square foot? At a much lower cost?

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Lets say, for example, that the heat transfer plates cost 5X as much per square foot as 1' of PEX. I don't see the cost/benefit in favor of the heat transfer plates!

I realize that more PEX = more manifols & higher head pumps.