Originally Posted by
Talay
Sorry, perhaps my terminology is wrong.
I mean that for a direct points purchase, the seat is available and for an upgrade of a paid seat, the higher class seat is available.
Paid seat is okay for upgrade, but Eithad may ask for several 100k miles instead of what the calculator says, regardless if a GuestSeat is available in the higher class (This is from personal experience).
They may also offer the calculator price, but it seems hit or miss. And you'll not know until after you've paid for the flight and then call the help desk asking for upgrade using miles.