Absolutely. I mean I remember 20y ago when someone's solution to spam was paying a small fee. Not what you want, but it's gotta be somewhere there. There has to be a cost to it, but it probably shouldn't be directly monetary. Submission delay might work.

How do they contact you? Email, social media, or LinkedIn? If LinkedIn, it is definitely not free. Recruiters pay a hefty fee for the right to contact people outside their network.