Struggling with pricing: Please help

I am creating a product on an accidental idea I had a couple of weeks back.

I created an MVP and posted a video of it in action on reddit and to my surprise it blew up.

Here is the reddit thread...
https://www.reddit.com/r/EntrepreneurRideAlong/comments/13xm1s5/i_made_this_seo_keyword_searching_thingie_for_my/

and the video https://www.youtube.com/watch?v=b-873SkJ2RI

I even posted a coming soon page where I collected some emails...
https://keywordranking.me/

Now I have more or less finished developing the product as a SAAS offering.

I have no idea how to price it as this field is new to me. Anyone with an SEO, content marketing background can help throw some light on it. What would be the typical pricing structure of SAAS apps in this feild.

Also, What would YOU consider a fair price for it as a monthly subscription.

I appreciate your help