I've yet to see any pictures of the interior so it's hard to know how widespread the damage is. However as I noted before, depending on the amount of fuselage damage, the most cost effective fix may well be to simply replace the tail barrel section with a new one. Problem is, it may not be practical to replace that section on-site (Boeing has some highly specialized ground handling equipment and tooling to transport and assemble those big barrel pieces in Everett and Charleston).
I wonder if they might do some sort of temporary repair just to make it airworthy, then fly it to Charleston or Everett for proper repairs.
I saw a TV show the other night that talked about the Qantas A380 rotor burst that said it took 18 months and $150 million to fix it
.
The other cost aspect is - if they scrap it, how long will it take to replace it. There have been cases where the damaged aircraft cost more to repair than it was worth, but the multi-year wait to get a replacement aircraft meant it made financial sense to fix it anyway. 787 delivery slots are booked pretty solid for the next five years or so - getting a replacement if this one turned into a write-off would not be trivial.
BTW that Egyptair 777 that they wrote off after the flight deck fire isn't a good comparison - it already had nearly 50,000 hours on it so it's value was much lower than if it had been a nearly new 777.