Ebay now has cheaper poly and rubber subframe bushings available. I'm not familiar with either brand (the poly brand is literally sus) and their significantly lower prices do not inspire confidence.

$149- 4 pcs Rear Axle Subframe Control Arm Mounts Polyurethane Bushings for BMW E53 X5
https://www.ebay.com/itm/284085972538

$32 each- REAR Axle Subframe Control Arm Mount Bushing for BMW E53 X5 33316770454 Single
https://www.ebay.com/itm/151586511703

If anyone's had experience with the more recent bushings please chime in. I am about to tackle this job.