The closest verified figures available for AI writing tools come from our internal AI tool database snapshot dated September 2026 — not 2025 — so treat these as the most recent confirmed numbers rather than a historical 2025 price list.
According to that snapshot, Grammarly Pro runs $12 per month, QuillBot Premium is listed at $4.17 per month on an annual plan, and ProWritingAid offers a Premium tier at $30 per month or $360 per year alongside a Premium Pro tier at $12 per month or $144 per year.
All three also have free tiers, and Grammarly's Enterprise plan is custom-quoted. The single most useful thing to understand before you compare these numbers is that a monthly price and an annual price are not the same product decision, and a lifetime price is a third decision entirely.
The mechanism that makes these prices hard to compare is commitment length, not features. A $12 monthly plan and a $144 annual plan can describe the same software, but the annual buyer is pre-paying for twelve months of access and accepting the risk that they stop using it in month three.
That risk is real for writing tools specifically, because they tend to get used in bursts — a thesis chapter, a job application season, a batch of client blog posts — and then sit idle. This is why the monthly number matters more than people expect: it is the price of an exit option.
When you see QuillBot Premium listed at $4.17 per month, that figure is an annual-plan rate divided across twelve months, so the true commitment is the yearly total, not the friendly-looking monthly figure. The same logic applies to ProWritingAid's $144 per year Premium Pro tier.
Here is where the arithmetic gets genuinely interesting, and it is the comparison the price lists never make for you. ProWritingAid's Premium lifetime plan is listed at $399, and Premium Pro lifetime at $699. Compare that $399 against the $12 per month Premium Pro subscription: $399 divided by $12 is 33.25, so the lifetime plan pays for itself after roughly 33 months — just under three years — of continuous use.
Against the $30 per month Premium tier, $399 divided by $30 is 13.3, so break-even arrives in about 13 months. Run the same math on the $699 Premium Pro lifetime against $12 per month and you get 58.25 months, or nearly five years. That is the whole decision in one line: if you expect to still be editing long documents in three years, the $399 lifetime Premium tier is cheaper than subscribing; if your writing need is a six-month project, it is not even close.
Notice too what the cheapest paid tier costs you in lost features rather than dollars — moving down a tier usually removes advanced checks rather than the basic ones, so the saving is real but it changes what the tool can catch, not just how much you pay for it.
Where this advice breaks down is that none of these figures tell you whether a tool is any good for your specific writing. Grammarly carries an editorial rating of 4.5 out of 5 in our database and is described there as context-aware, adjusting style for academic, business, or email writing and offering Smart Drafts; QuillBot also rates 4.5 out of 5; ProWritingAid rates 4.4 out of 5.
Those ratings are close enough that price and workflow should decide, not the score. Prices also change frequently — the only reliable source for today's number is the vendor's own page, and the snapshot here is dated 2026-09-18. One practical tip: before buying any annual or lifetime plan, export a sample of your own real writing and run it through the free tier first.
Free tiers exist on all three tools, and while they limit how much you can process and which advanced suggestions you get, they are enough to tell you whether the suggestions fit how you write. Paying for a year of a tool whose advice you ignore is the most expensive outcome on this page.