The main reason behind this in roleplaying games is for game balance. Cyberware can really pump up a characters abilities and lethality along with making them damn hard to kill at the same time. So making each bit a risk of sending the player character off to NPC land as a raving lunatic does make one stop and pause when thinking of the chrome warrior image. The question is how do you handle it differently or what do you put in place to replace it?
This time I'll focus on the handling it different part. No hard stats for games or anything, just some thinking out loud on the subject.
Very first and foremost should be Why. Why is the character getting a chunk of machine added to their body? To me this is the big one because if I lost my arm in a car wreck but was able to have it replaced by a working replacement that moved and looked just like my original arm, well I would be seeing that as a miracle of modern science and be happy about it. Now by the same token if somebody opts out to have a perfectly good limb sawed off and replaced.... well they probably had some mental problems to begin with.
Cybernetic replacement by necessity due to injuries or health problem shouldn't be a huge hit to ones mental well being. Sometimes it may even increase their mental stability by improving their quality of life. While cybernetic replacement for the sake of getting a metal part should be a bigger kick in the brain.
Now my second thought is on common cyberware that many people receive to perform daily tasks easier or for a job. Things like a neural link, data plugs, neuralware processors, etc; these would be something popular culture would make readily available with society ready to accept them as the 'next big tech to improve your life' thing. Getting something that nearly everybody else has shouldn't make you feel less human or unhinge your psyche. Especially if they become needed for a workplace, using advanced equipment and competing in the job market. It's an edge that shouldn't cut you back.
Other pop culture fueled cyberware range from the glowing tattoos, implanted time displays on your wrists, or even having the color of your eyes change. It's what the latest reality television star has along with the new wave of rockerboys coming onto the scene. They're popular, their cool, their neat. Why would these cost some sanity again?
Finally the last thing on my mind is all the other stuff. The things that aren't replacement parts or pop culture bling. Subdermal plating, wired reflexes and adrenalin boosters. These seem to have one focus in mind and that's to make you better at the job of hurting other people. Either through making you faster, bullet proof to a point or just the ability to pull out a gun faster than most people can blink. This is a tough one to make a call on. One could say the person who would get these things may not be in their right mind already, but another could also counter that with the fact that it increases their ability to survive, a base instinct.
So my end thoughts on this would be that I would definitely use the 'Why' as a modifier for any sort of mental affect. How much detail you would want to work into the rules for this is completely up to the ruleset I suppose. That or you could simply do the GM 'handwave' and say no loss for replacing something that actually needed replacing.
What are your thoughts on all this?