I'm curious about the uptake rakers life as well. With the boulders it ate up in the last part of the video, that's gotta be some stressed steel.
The bearings are probably all readily replaceable like the pillow block shown by the hopper. A couple hundred bucks a year in bearings would be a small price to pay for the time savings of that sucker vacuuming the field clean every spring.
Here is a self propelled rock picker, when they first came out with this I think it was around $100 an acre and a minimum of a couple 100 acres. They have made some changes from 10 years ago, I wouldn't be surprised if it costs more now with a bigger acreage requirement.