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Here is a unit from Mancini that includes the control arms and what not. I believe this is made by CAP for Mancini but I'm not sure retails for $2300
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Then you need to compare apples to apples. "control arm and what not" are expensive. And Mopar ones with T-bar provisions are more expensive to make that the Chevy A-arm with spring perch bucket. Two Mopar LCA should cost about the same or more than the custom K-member in regards to manuf costs.
But I get your general idea. And the cost difference is due to volume.
Next question is why do you feel the need for a custom K-member that has the T-bar arrangement. You're not going to get the header clearance gains from removing the T-bars nor better selection and cheaper springs.
The weight loss is mostly due to the rack. I see the going to the rack as the biggest gain, by far, in the tubular K's that retain T-bars. All that money for a rack.
Racks are nice, lightweight and precise. But the rack alone is not the Second Comming of Christ in terms of road feel and response.