I would also say that the FORM of the material component doesn’t matter in terms of perception, but it can still be perceived per Jeremey Crawford’s tweets. It doesn’t matter if you are using a focus or material components, because either way they can be perceived.
The part that you are missing is this:
Sul will kill you before you can planar bind them. If you stand in front of them they will not just ignore you. They will kill you, and with one hit point it wouldn’t be hard. Especially because invisibility and Mind Blank don’t foil true sight. Which they...
It is worth noting that while the Sorcerer might not be the indestructible demigod he was made out to be, @Hohige has roused a vigorous conversation and continues to bring us unique and exciting characters to discuss!
Jokes aside, it was really fun reading about this character and I can’t wait...
Ahh, how could we have overlooked the foolproof strategy of Twin Subtle Quicken Empowered Wish cast 5 times a day to control any creature you want? All while never getting hit once? Foolish of us!
So why would Sul not just Legendary Resist? I read a bit from before but it would seem that the Squishy One thinks he can last even one round in order to burn through Sul's Legendary Resistances. Let alone 3 rounds.
To be clear, if you are casting a spell that requires costly components, such as planar binding, the casting is NOT imperceptible. Sul would not just sit there and watch as you sprinkle ruby dust at their feet. I will provide sources as it seems @Hohige doesn't like sources themself...
So he is saying he is going to Planar Bind Sul-Katesh in order to not be killed? How is he going to last an hour standing next to Sul-Katesh casting Planar Binding?
edit - (Sul will kill the Squishy One with an unarmed strike)