At What Point is a Solid Cam Better Than a Hydraulic Cam??

It is not the oil, never was. There is still enough Zn/Ph in the oil to do the job. A little known fact is that the Zn/Ph gets 'used up', one of the reasons for regular oil changes. You don't see cams/lobes wiping out at the end of the oil change period because of reduced Zn/Ph.