its honestly impossible to guess hours on a machine based on wear of a pin/bushing, as you have no way of knowing how often it was greased or not, which can change life span of them, by a huge margin! say a it was not greased that often and used in a dusty sandy work area! , it can wear things out way faster than one greased every 8 hrs of use or more often in a more forgiving environment! ! and you have no way of knowing if there high quality pin/bushings, or cheap china made ones!
and if your trying to age use on a machine by these pin's/ bushings, that too is impossible, as you have no way of knowing if there original ones or not!
many times they could have been relapsed, and then , you have no way of knowing if the pin's /bushings were replaced with high quality one's or cheap china junk!
so honestly its not possible to judge hours by them
better way to tell hours on a machine, is over all wear and tear on many area's, , and if possible a compression test on engine wouldn't hurt to give you an idea on where its at in its life span!
how a machine is cared for and used, can some times be a better way to judge a machine, than just by hours too!
a machine with low hours abused and never cared for,(lack of greasing, oil/filter changes, and or an abusive operator running abusive attachments) and or used in a bad environment, can be a bigger problem child, than one WELL cared for with twice the hours on it IMO, with in reason of course! ,
or thats just my 2 cents!
Hours alone will never tell the full story, seen brand new like machines get sunk, cleaned and sold, and the likes, so LOW like new hours on them, don't always mean its a good buy!