Heavy loads isn't the only reason to use the factory setup. The cost includes a 6,000 lb hitch that's integrated into the vehicle properly, where all the other receivers require drilling holes in your chassis. Plus the factory assembly includes all the necessary electronics so you don't have to hack up your wiring harness.

If you found a used one, then try to get both the hitch and the wiring harness which is in the spare tire well.

For me, having installed my own hitch, I can see why this is rated for 6,000 lbs. and the others aren't. It's actually a structural part of the car.

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'04 E53, 4.4 Sport
'97 E39 528i
'86 911 Carrera, track car
'96 BMW R1100R