I got 77 packs for $55.
Buy 40 pack for $50, get 2500 coins (worth $25).
Buy 15 pack with 1999 coins, get 1000 coins, have 1501 coins.
Buy 500 more coins for $5, have 2001 coins.
Buy 15 pack with 1999 coins, get 1000 coins. Have 1001 coins.
Buy 7 packs for 999 coins.
Have 77 packs and 2 coins left over.
7 legendaries, one golden.