Thanks for your responses all.

I guess from seeing them and thinking further it is more a case of how many miles do you need to not worry about the question...

EG if I had 1M in each program plus was earning at least what I was spending in them each year then I would never use cash for Hotels or Flights...Elite Status wouldn't apply if I was redeeming in F/J instead of Y.

But when I haven't got that amount, where is the tipping point where it is worth paying.

Tricky subject... the maths are there though, I can kinda visualize it so will think some more and see if I can excel sheet it, any other insight would be appreciated.