Wasn't there a problem with their promotion regarding finances? IIRC Sid Lowe had some article on how they were actually going to be punished for acting within their means.
Well, it wasn't quite like that. As barmy as it is that a club with no debt could actually find themselves demoted rather than justifiably taking their place amongst the elite, this comes down to a law introduced well over a decade ago which requires all clubs which play in the national 2nd Division to convert to a limited company and expand their capital to a level based on averages for clubs in that division.(this average therefore includes clubs like Depor, Sporting, Mallorca, and Zaragoza which are massive in comparison with Eibar).
Obviously to anyone who follows Spanish football this law has completely failed to keep clubs out of debt, and therefore has rendered itself utterly useless, nevertheless it is absolutely not a surprise to any club which gets promoted from the regional 2B leagues. In fact, Guadalajara were demoted under this rule at the end of last season (the beneficiaries of that decision were the incredibly debt-laden Real Murcia) and Alcorcon and Mirandes only just escaped demotion by finding enough capital at the last minute.
So, I sincerely hope Eibar find the 1.5 million euros (I think) they need and take the place they've earned. But if they don't, as morally wrong as that might be, they can hardly complain too much because they knew the financial rules for promotion well before the event.