great post, rakso,
you must be an analyst of some sort in your real life.
I am in the design field, so my approximated calculations are already good enough for me

Anyway, different people will look at this differently. For me, I would rather fly 2 times rather than 3 times. It also depends on how one tolerates long flights. I personally can't endure 12 hour flights sitting down with 3 people next to me and worse, if it is overnight. To me there is a huge leap from economy class to business class and my subjective valuation places the increment not at 50% more, it is 150% more. It is a leap from a seat to a bed and not to mention the wine and dine experience in the front cabin. Of course, all this is subjective. I am not sure if you can analyse it by placing a cost value.

As for the Manhattan card, again, it depends on individual. For me, I love travelling very much, and I would like to see the world - far and near. And for those far ones, I am depending a lot on these miles since I won't be able to bear the 27 hours to Sao Paulo in Y class as an example . So I have been focusing all my energy and resources to accumulate them - I am not interested in any other rebates of any sort. So for me, it is Maybank Horizon, DBS Altitude, and Citibank Rewards only. And so far, first class seats have been within reach for the last few years.