I would like to preface this with I do enjoy grinding feed, but when I am short on time the way it is I figure why add more to the headache and in our area pretty much everyone went from grinding their own feed 20 years ago to the coop grinding all the feed.

I look at the time aspect: grind 1 load and it takes 40 minutes, 2 loads 60 minutes, 3 loads 80 minutes, etc.  Starting the tractor, hooking up the grinder, etc is half the battle so unless I would grind 3 loads at a shot, the time per load is just too high.  Having a dedicated grinder tractor would make like simpler, but that is another tractor to maintain and takes more shed space both of which cost money, not to mention that now I need a 40ton bin for DDG, a 20ton bin for pellets, 5T for SBM, 5T for cotton seed, built a shed for minerals and bags.  By the time you factor the overhead of the support equipment for the grinder into the equation it does not look as appealing as just the cost of the grinder.  I suppose I could get by with smaller bins to save some overhead costs, but now I don't get the savings on the DDG and pellets.  Not to mention once you get to the point of grinding 10-20 loads per week then it starts taking the better part of a day which means even less time.

I am open to the idea of mixing our own feed, but for now I pick up the phone, order 15 tons of feed and try not to think about the $150 (realistically $40-50) I could have saved and remember that a new mixer grinder is over $40,000 and support equipment is going to run another $10-30,000 and it will take a lot of tons of feed to pay for a new grinder and equipment and that all the used ones are all pretty much wore out or rusted out.  The reason new grinders cost $40,000 is because they are not really a cheap piece of equipment.  Sure I can go out a find a $1000 grinder and then dump another $1-2000 into it and get by for a few years and then repeat the process.  The trouble is finding that good one for $1000 vs buying an okay one for $5000 and still dumping some money into it.  The cheap ones are out there but there are not near as many as there were 10-20 years ago.  Several of the grinder mixer OEMs quit building them for a while and now a few have started building them again.  I attribute that to the fact that most of the good used ones are now gone and the guys grinding lots of feed are being forced to look at new for their next replacement.

The reason Christensens and other integrators don't have farmers making feed is it would open them up to a huge liability and also be a nightmare to manage.
They also have an advantage of dictating the price of their feed when bidding on grain vs paying what the farmer wants for his corn because "it is there".  They are not the only hog operation that has moved away from PTO mixer/grinder to an electric mill.  Most all that do cite the lower cost of feed and better quality as the reason and have indicated that they should have done it sooner.

FWIW I know several dairies that purchase ground corn for their milk cow rations because they can not get a consistent enough grind out of a mixer grinder to hit 400 microns or less.  Half the local mills can not even grind that fine, so the few that are are picking up a lot of dairy customers and doing it reasonable to move enough tons to justify the investment.

I won't say that your story on the 60 hp electric motor isn't possible but you'd have to put a huge pile of grain through that machine for it to save enough $'s on electric vs diesel to make a payment on a new tractor.
It is possible the owner may have been referring to the annual payment to trade tractors not outright buy a new one, but at the time he was moving quite a few bushels per year.  He did comment that with far less hours on the tractor that he planned to keep the tractor longer and at the time had been trading every couple years; that was 10 years ago and I am pretty sure he still has the same loader tractor today that he did then.  The fuel savings for electric is huge but is a drop in the bucket compared to depreciation and maintenance of a tractor and at that time a $6000 electric motor was able to replace a $100,000 tractor.  Sure he could have gotten by with a 4020 at which point the $6000 motor would have replaced a $10,000 tractor, but the fuel savings were still there to replace the tractor every few years.

In all honesty, grinding feed is one of the most profitable things I do vs the cost of hiring it done and trucking our corn to town.
I know how everyone on here advocates grinding feel because it is one of the most profitable things a farmer can do, but how many are willing to grind/mix/deliver to another guy for under $10/ton?  I can not seem to find any that would do that and that makes me question is their cost really that low and if it is worthwhile to attempt to grind feed for a few thousand dollars per year savings.  If I had 10s of 1000s of tons every year to grind it would be a no brainer.  For a couple thousand I think ago it.  For a couple hundred or less it does not make sense unless you can get into a good cheap grinder and support equipment (under $2000 total investment).  The big advantage of grinding lots is buying all the feed stocks in bulk and that requires bins large enough to accept a semi load of ingredients.  Buying 10T of DDG will cost the same as buying it from the coop, buy a semi load and save some money.