Complex sentence: The Russian and Indian air forces plan to purchase about 250 FGFAs each at an estimated $100 million per fighter for an $25 billion total for each nation, in addition to the development costs.
Split into simpler sentences: The Russian and Indian air forces plan to purchase about 250 FGFAs each, at an estimated cost of $100 million per fighter. That adds up to $25 billion from each nation, in addition to the development costs.