Russia is many years ahead of China in the field of helicopter development, they have a lot of experience and technology. The Chinese z-10 is not inferior to the Mi-28, but the Mi-28 has its own advantages. Another reason is that China does not have any helicopters similar to the Ka-52. Coaxial rotor is the weak point of China.
Buying weapons from Russia and receiving TOT, China can use Russian technology to continue to improve its weapons. They can integrate the technology of the Mi-28 into the Z-9 or z-10. Or on the basis of the Ka-52, China will develop a more advanced version of coaxial rotors.
The same is true if China buys Mig-35, Su-35 and Su-57 with TOT
Buying weapons from Russia is not just for technology, it is also a political message to Taiwan and the United States.
Every time the United States sells weapons to Taiwan, China will buy weapons from Russia and receive TOT.
Taiwan realizes: they buy weapons that make China stronger and make them weaker.
The United States recognizes that arms sales to Taiwan are benefiting their two enemies. China has technology and Russia has money.
If the US does not sell weapons to Taiwan, China will buy less weapons from Russia
If the US sells weapons to Taiwan, China will buy 10 times more weapons
Enemies of the enemy are friends. Helping an enemy's enemy is the most effective way of hurting an enemy.
Are you serious?
Su57 still in low numbers. Where as J20 is flying around in numbers. Look at the ships of the Russians. Still deploying Soviet ships.
Where have you been hiding for the past 10 to 20 years.