That chart pretty much sums up the situation however the bike he chose IMO doesn't represent the typical darksider.
To me the classic darksider is the owner of a pre 1800 Goldwing. There is a savings on the tire but also the amount of work to R&R the luggage to access the wheel. I do my own wrenching so don't know the cost of the luggage removal and replacement. Let's assume $200. That could be light.
For a high miler 1500 Goldwing using guesstimate numbers:
Conventional: A $200 tire every year plus $200 Install = $400 a year
Darkside: A $100 tire every 4 years and one $200 install = $300 for 4 years = $75 a year.
Over 4 years the darksider spends $300 when the brightsider spends $1600. $1300 in the darksiders pocket. $325 a year
HOWEVER we aren't looking at the whole picture. Tunnel vision sets in focusing on $$$$$$.
When you change the rear tire on a Goldwing you normally moly lube the splines. I can't recall the mileage maintenance number for this but if you do the lube with a normal tire change it's unlikely that you will ever have a problem. With the wheel off the lube is a few minutes.
Going darkside, a responsible owner should still pull the rear wheel and lube the splines at a cost of just a little less than changing a tire.
Rehashing the 4 year darkside tire savings with proper spline maintenance, the $ 325 a year savings is more like $150.
I'm with Wingboy regarding the fridge falling off the truck. I'm happier with sticky new rubber designed for the job, not 4 year old hard from the get go car stuff.
If you ride solo and want to chance a car tire it's your call. Many are happy with that choice and I wish them no harm.
There are unanswered questions:
To my knowledge there is no M/C tire for a Goldwing that will satisfy load limits for Bubba, Chubby Cheeks and a trailer. A car tire trades traction for capacity and could be safer. There are parties that are interested in doing legitimate studies and there are parties that could afford to do the studies. Unfortunately they are two different parties with two different agendas.
Is there a technical reason why run-flats aren't available?
From what I hear, they aren't cheap but if a $500 tire keeps you from needing your $1000 helmet.............................
Feel free to correct my numbers.