Well if you get the ones that are acoustically flat (or almost) itOK, I'll ask the question...
I just use the disposable foam ones that have an NRR of 32. They seem to work very well for me... lots of noise reduction but I can still hear my Sena, horns, sirens, etc.
What makes the custom ones worth $100+?
s great to be able to protect your ears and still hear pretty naturally. If you go for the generic silicone/latex mold solids, not so flat but not much different then foam expendables.
Advantages: Comfort, hygiene, speed. After rolling the foam ones between my fingers more then once or twice you have to wonder what all they are picking up. Time to insert and protect, about a second and half per side.
Ultimately what is the best hearing protection?? The one you will consistently use!! Period, nothing else. If not consistently used then everything else is a mute point.