10 ingots.
Asuma is 15 points per piece.
So it's 15x80=1200.
Let's assume you'd get approximately 3.7 points per key.
Then it'd be 324 keys for full asuma. -77 keys you can get for free. So it's 247 keys or 2470 coupons/ingots for full asuma. Most people already have a lot of his fragments so it's gonna be way cheaper for them.