Gemini offers a free tier that handles day-to-day writing and brainstorming...

https://smoothdecorator.com/gemini-pricing-for-marketing-work-what-plan-is-actually-enough/

Gemini offers a free tier that handles day-to-day writing and brainstorming with ease. If you are a power user or professional needing deeper capabilities, the Google One AI Premium plan costs $19.99 per month