SEO Tools under $10/mo?

I'm trying to find some SEO tools in which I can help out a friend with his small business. I realize the good tools (Ahrefs, SEMRush, etc.) are expensive for a reason because of their robustness, but I'm just wondering if there are any tools out there that are worth trying at a smaller price point, be it for backlink tracking, keyword research, keyword tracking, etc.

I'm aware of some free(ium) tools like Search Console, Ubersuggest, Ask the Public, but anything you've liked or enjoyed, I'd love to hear it!