Mrs. CO FF is coming with me on a trip LAX-JFK later this year, so I looked at fares that would be good for a GLD challenge (she lost her status at 21k BIS last year).

In mid-August, I found fares (o/w, pre-taxes) on a variety of dates as follows:

$259-$299 -- cheapest "Economy Supersaver" fare, depending on time of day
$329 -- the next step up after the cheap seats went, still "Economy Supersaver"
$965 -- "Economy Saver" fare
$1,555 -- "Economy Flexible" ("Y"/"B")
$1,217 -- "Instant Upgrade" (K-UP)
$749 -- "Business Special" (books as I)
$2,178 -- "Business Flexible" (books as D)
$2,497 -- "First Flexible"

The $259 fares tended to be the first/last flights out. Most flights start at $299. Now, given fuel, those low-end economy fares don't seem all that outrageous to me.

But I can't understand why the K-UP is 60% more than the "I" fare, or why the "I" is half the Y/B fare.

Any ideas?