Id like to add, a part of the equation will also depend on if you fly alot and enough to get even the 1st level of Status which by most Programs means 25k a yr in actual flight miles
also keep in mind that usually an Intl flight will cost more then a Domestic flight. with AA for 40k a person can get a free coach tkt to numerous European Countries between 10/15 - 5/15 Inclusive. An example is the trip I took to Belgium in May I left on a Sun and returned that Thurs = 3 nights, it would have cost me $2200 to have done that otherwise, if you stay over a Sat then it was apx $600
also every year before this one I was able to get a NY-LA tkt for <$300 for July and Aug its hard to find anything for <$500, so if I had to be out in LA then a good chance Id use 25k this yr to fly for free if it was available, something I never would have done when the fare was <$300. 1 last item is at times its good to set a goal for your Miles, eg a tkt to Israel , I used to purchase my tkts there but havent in a couple of yrs, simply because it became too expensive per mile wise, where it used to be 6 to 8 cents a mile its now apx 12 cents. So I can either pay for the TLV tkt and earn 11,400 miles from NY or use that same $$ and by flying to the West Coast earn apx 28k miles. Now I fly to TLV a min of 3 x a yr, so if aperson will only be flying say 1 time ayear on their vacation then their accounting should be way different then mine, But they too should work out where theyd like to go using their miles and then apply the formula that SF was so kind to post above
