Originally Posted by
appleguru
Up until a few months ago, it was "only" 25,000 miles. Seems to be absurdly priced now, but since every flight seems to be different, it is really hard to say.
25,000 miles (each way), was the number of miles required when you
purchased M fare or higher. Now you can upgrade K fare or higher, so it requires more miles. The number of miles required for upgrade is based on your original booking class.