lol if only it were that easy.
Heck, even had one code challenge pre-interview a few years back at x2-x3 the salary I was aiming for at the time, for a C++ role, even though my total experience of C++ is half of one job that I only stayed in for about 15 months. Obviously I didn't get that interview let alone the job, but that's why they don't just rely on the contents of self-promotion documents we write and which they barely read.
I've had a few messages saying "you won't get many offers with that rate", which is kind of the point! That being said, if anyone seriously did offer me fifteen large for each of the three days minimum (two travelling days, at least one working day) then I'd take it...
Don't say "No.".
Instead think about it, figure out how much it would be worth TO YOU to do the thing, add some, and quote that.
A friend with his own firm/ consulting practice was an expert in a particular kind of database work, was asked by IBM to do a months-long project in Turkey (iirc). He didn't want to go but used this approach. A week later he was in Turkey (they didn't even blink at his outrageous quoted price). Said it was totally worth it because he'd taken that approach.
Bit if you're just looking for validation from the internet to not be polite, then here you have it - it's ok if you don't respond to a recruiter who you don't want to respond to.
Spam does not deserve a polite response, and responding to spam is, in fact, detrimental to the rest of the Internet and rude to the rest of us using it.
So you are being rude when you do respond to spam - and including LinkedIn spam.
The companies that such people are attempting to recruit for, probably share my dislike for those that can't tell the difference between platforms or languages.