With all due respect Ken, you are incorrect on virtually every point made. Let me break it down.
"first and most importantly, railroad pricing is either railroad equipment or private equipment."
First, maybe. Most importantly, no. Actually, car cost is a relatively small portion of the total cost to move rail freight from A to B. As such pricing differentials between railroad equipment and private equipment are certainly not the biggest cost factor to consider*.
"in general, the difference allows private equipment to be paid-off in 2 years"
Wrong. Dead wrong. The rate differential has NOTHING to do with expected pay-off. It reflects the differential between what it costs the railroad to provide the equipment vs. the cost to the railroad to operate a shipper's owned or leased car. To show how preposterous this statement is, a new tank car costs ~$100,000. Not counting interest, a two-year payback would be $4,167 per month.** It's surprising you would believe this, as you're an accountant, no? Do you depreciate 50-year assets over two years?
"further you assumed the difference in cwt reflects the equipment gwr.a logical assumption except when you deal with railroads. A 220k car can carry 70-90 tons, a 263 can carry 90-105 tons and 286 - 101-116 tons depending on car ltwt. the pricing you claim saves 5% actually costs 14% more ( $2175 v $2466 per car).
I'm afraid it's logical because it's correct... even when dealing with railroads! You are confusing gross cost with unit cost. This is no different than buying milk. I'm thinking most folks probably don't buy milk for the family by the pint. Though a gallon of milk costs more than a pint, the gallon is MUCH cheaper on a per-pint (unit) basis.
By the way, there aren't many (any?) 220K cars that can carry 90 tons. The range is more like 70-80 tons. Your 263K/286K capacity ratings are closer to the mark.
"frankly, there are no railroad mechanisms to determine cwt weights so this relies on shipper statement."
Correct, most scales are a thing of the past. And many of today's rail rates are in dollars per car. In many industries, however, it's easy to corroborate shipping weight estimates using weight per cubic ft or gallon coefficients against a cars cubic capacity.
"look at the pas tariff 4127.2-a to see rail v private equipment car differences"
Exactly. This confirms my earlier comments re railroad vs private car cost differentials. The average differential (to Maine points, at least) is ~$250. Considering that the car would cycle from interchange to destination and back to interchange in about 2-3 weeks, that differential closely matches what a lease rate would be for a high-cube covered hopper.
* in the case of PAR 4127.2, railroad-supplied car cost component is about 11% of the rate.
** in the case of PAR 4127.2, $100,000 new covered hopper car cost divided by the $250 savings per trip would require 400 trips to recoup car cost... at 12 trips per year, that's 33 years. In actual fact, shippers typically lease cars to match the asset obligation with the business opportunity.