Sure 2.5 billion dollars is a large sum of money. Imagine how you'd break this news to the public. You've practically crushed people's hopes and dreams. "Umm, guys, we just accidentally bricked the rover because of a firmware upgrade gone rogue". I'd end up in tears if I had done this.

Speaking of firmwares, I'm unable to find out information if they have a dual bios kind of system where if the boot fails it can recover from the backup firmware.