It was a very basic and overly simplistic calc, the savings are...

It was a very basic and overly simplistic calc, the savings are partially due to reduced handling costs, but part of the savings is also due to not having to maintain the NOSTRO accounts which represents an opportunity cost. XRP should be cheaper than NOSTRO ($270 equivalent) since the tokens can be re-used multiple times per day, but complicating this are facts that a large proportion of XRP might be privately held and not available free float on any given day to facilitate transfers. We don't know to what extent banks/financials/market makers will seek to stockpile XRP to ensure enough is available. Still the cost needs to be high enough to enable single payments >$1 billion.

I have found another analysis by somebody far better qualified and cleverer than myself, their estimate for XRP is $151.51, so I'm not too far off at least. You can check the link for their basis for this. I found the link referenced in Hodor's XRP blog, which is good for a read. Best wishes. W1