Not a lot of info out there...
It's been reported that Fire Emblem Awakening would have needed to sell 250K to continue the franchise.
So... 250K would have been just about 10million in revenue. About 1/5 of that would probably be gobbled up by retailers. Meaning 8 million would have been profitable. There's also other non-development costs like shipping/packaging, etc. Based on that, I'd guestimate the budget at somewhere around 3-5 million, but that's just speculation. And obviously games on Switch are generally going to be more expensive to develop.
250k does not seem enough pay all bills. I'm assuming with 250k was the minimum it needed to sell so they could try again, even with losses