Like anything that "costs more", the quality and workmanship is better. After that three things come into play.
1. Is the performance increase worth the cost ?
2. Does the task warrant the better quality and performance ?
3. Is your skill able to take advantage of the better quality performance ?
Yes, a Pickup truck gets you to BurgerTown as fast as a Ferrari, assuming your subject to speed limits .... but is that the only criteria ? Certainly not in the same comfort.... and if ya going in the Ferrari, 1) Burger Town is not your likely destination and 2) your date is likely to be a bit more discerning about the places she eats.
I find a $19 mouse just about useless ... it doesn't have the precision and features I need for CAD and in gaming, I will die a lot more. A $95 mouse sits better in the hand, has a heft to it and lets ya get in a good days work w/ o fatigue. OTOH a $35 mouse does almost as well.
As for KB,s one of the features which I find useful are the LCD displays which I use to monitor system information. Tactile feel can significantly increase typing speed and accuracy which brings real cash returns in a business setting. Having extra sets of keys for game macros is a benefit many gamers wouldn't give up.
And while, I prefer the feature set of a $140 one, I am perfectly comfy working on a $45 one. A $19 one however costs me money and I find it cumbersome and unproductive.
There are many things in life that don't impress from where you are sitting. At 18, a $2 bottle of wine got me the same buzz as a $12 one. But, as you gain experience with better components or better anything, you gain the knowledge and ability to discern the difference.
Of course there is a point of diminishing returns.... the more money you throw at something, the lesser the amount of improvement that can be gained. No sense spending more than ya need if your task needs and ability are not capable of taking advantage of it.