If you want to buy Praying Mantis Blades from the ripper, you have to spend a decent amount, and the legendary version of the blades is many times more expensive. But in Cyberpunk 2077, you have the option to get them for free.
To do this, go to the center of Knight City, and in the west of the "Plaza of Corporations" area, take the side quest "Attack of Cyber Psychosis: The Ghost of Night City." Once in the quest area, on the right side in front of the garage gate, you will see a chest in which the blades lie.
After you get the blades, you will be noticed by the Cyberpsychopath. This opponent is extremely strong, but you can simply run away with the loot.
Then visit the ripper and attach the legendary Mantis Blades. Combined with an implant that slows down the time the enemy sees you, you get a very deadly melee weapon. The advantage of the blades is that they become stronger over time - the attack power depends on the character's level.
