They might be sourcing the part from a mfr in Taiwan and marking them up because the aluminum ones on eBay are about $35. Their design is also made in a way that it can replace earlier bushings.

I've tried to understand why MB would use plastics for this part. The bushing itself just fills the space and only turns as part of the assembly. Nothing actually wears out, the bushing just disintegrates. I'm not sure when CNC was viable for mass production. In the early 80's a chunk of aluminum that shape could have been cost prohibitive.