The purchasing price per aircraft is estimated at $83-85 million. The total contract worth is around $2 billion and also includes ground equipment, spare parts, and other Russian logistical support.
China is interested in the Su-35 for its AL-117S turbofan engine. Russia has repeatedly refused to sell the engine as a stand-alone product, which left the PLAAF with little choice but to acquire the entire aircraft. The Chinese military aviation industry is still struggling with designing and building an engine for its new fifth-generation stealth fighter prototype, the Chengdu J-20.
Both of China's J-31 and J-20 stealth fighters are incapable of super cruising at sustained supersonic flight.