i get this alll the time.
I used to spend days talking with potential clients only to realize that they are not even interested in paying a fraction of my rate.
So what I do is, before we even talk about anything, i ask them to familarize themselves with my profile and specificlly about my hourly rate (I have a note written that i just copy/paste). So this way, we clear it up right away and my time isn't wasted.
Make use of them. Practice the skills of positioning work, negotiating rates, and seeking higher value for your work. Of course it is probably "all for naught" as there are clearly a significant percentage of prospective clients out in freelancer-land who are bottom feeders.
Play to win. Play the game to learn and expand your skillsets. Make use of their time as a no-charge training ground. Use rough verbal tactics.
"I see you are seeking talent at a limited rate. There is the obvious reason to assume that low-ball work returns low-ball results. I ask a simple question. How important is success in your project? How much is it worth? With my services you will pay a fair price. I specialize in superlative delivery and provide back work well worth the cost. Perhaps you should adapt your strategy. That's option one. Option two, I will apply again when a low-ball resource craters your work and it is time for a do-over".
You are welcome to copy those words ,cut-and-paste them into each of the lowball bottom feeders, and interrupt their day with a bit of thoughtful messaging.