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[sternwake]

The $63 agm won't start any real size diesel, ........................

Note, I 'wrote' jumpstart a diesel, I was not implying such a battery, by itself, could start a diesel, and certainly not a huge diesel.

Whether it could help jumpstart a diesel depends on the actual state of charge/healthy  of the batteries this AGM would be assisting.
And other factors of course.

My 18Ah AGM would not jumpstart my friends sprinter, whose group 49AGm  delco was down in the 7 volt range, way beyond dead. but if it were in the 10.8v+ range, it would have, I bet.

My 18Ah AGM has, by itself, started my 2 week cold gas 318, when new and in warm ambient temps, but it was close. 

It is a good deal, for what it is. NO argument.
I guess I don't like what it is though.  Opinion.
Depends on the end users end requirement, and expectations.