In games where you have a point based character creation system and various settings, like gurps, d20, etc, you can have settings where players can actually buy improvements to their characters with money instead of spending character points to get them.

So, if you're in a game world where you could buy, say, an implant system that gave you new abilities or improved your character with nothing being spent but money (Like, say IR eye implants or a muscle stimulator that caused yur muscles to twitch in your sleep as a form of exercise that boosted your strength and endurance) do you think that players should be able to buy or otherwise acquire them without any expense besides money?

Some GMs want the players to spend the money and the character points as a matter of game balance. Others tend to think if the world you're playing in allows you to buy things like upgrades with just money then that's part of the world setting and shold be OK.

 I'm Ok with players buying things to improve their character unless it reaches the levels of pure asshattery. Sometimes it can go too far, like the player who buys wealth, then uses it to buy every ugrade in sight to turn himself into roboPC, but a good group can deal with that.

The main systems I've come across that allow purchase of body improvements (bioware or cyberware) had some other balancing factor like Empathy or Essence.

The current homebrew system I'm playing allows character points to buy cyberware without any risk in surgery (or paying a financial cost), but if you spend just money then there is chance of complications in surgery leading to stat damage or even a chance of dying on the operation table. Also it's stupidly expensive, so character points method is much more attractive.

Generally people will buy the simple stuff like fashionware but if it's messing around with your nervous system, muscles or senses they will spend character points.

I prefer games with a wealth score of some kind, so it all works out to be the same.  Buy your improvements with character points, that's less points that you would have to put into resources.  I generally don't like keeping track of exact amounts of money.  Too much bookkeeping -  just let me know if the characters are poor or rich.