factory aluminum trunk lid... check this out

I'd think using 73 brackets would save more :D

Absolutely, especially after removing the brace/reinforcement in between the bumper and "regular" bumper brackets. But that is a considerable savings for those people who may not want to do the work to replace the "shock absorber" brackets with the "regular" brackets.

The regular bumper brace/reinforcement is sandwiched with the same bolts. The later bumpers with the "shock absorber" brackets need the brace to bolt up. None of the early parts interchange with the later parts and require fabrication to mount to the frame when changing either way.