32m is needed. Castle level 3 gives 3m Arms item gives 3m Shoulders gives 5m Sickle gives 1.4m (Sword would give 10% of 6,737,200 -- so equip sickle) Gloves give 2m Hooves gives 700k Boots gives 3% (~200k for CoE lvl3) So that's 15.3m possible from items, leaving 16.7m bfa needed from allies. Ally market prices will always fluctuate, but cheaper allies will usually have a lower "price per combined stat". So it's easier to quote the figure in this manner -- you would need 250 allies with 67k attack or higher to hit Haunting without pots. Without items and only the castle upgrades, you'd need 29m bfa -- 250 allies with 116k attack or higher.
Yeah it's been tested and found to be roughly 32mil BFA to get all 24 to 26 hits in with no troop loss. Even some large attack builds can loose their last 1 or 2 hits if they don't have a decent bfa.
Its not about just scraping pass the minimium to hit eb. If you are just scraping pass the minimium, you will be losing more troops per attack although its a success
I think or sporavek's revenge you need around 60m to hit. I start losing more troops with 14m bonus from attack buildings, 4m bfa, 23m from items, and 25m from mith.