I use mine for *A business class rewards, so I get a very high c per mile figure if I do the straight comparison. However, I would never buy such tickets myself - I'd buy the cheapest Y tickets, so the alternative calculation would be the $ cost of the economy ticket divided by the number of miles used - a massively lower c per mile figure. But then I get great pleasure out of the C ticket whereas I would get great pain out of the Y ticket. So the true number is somewhere between the two, but I haven't the faintest where.