The price gap between AI writing tools comes down to what each plan actually bundles, not how good the underlying AI is — Grammarly Pro runs $12/mo while ProWritingAid's Premium tier is $30/mo, and the difference reflects different feature sets, not a quality ranking.
According to our AI tool database, Grammarly Pro costs $12 per month, while ProWritingAid's Premium plan is $30 per month or $360 per year, with a cheaper Premium Pro tier at $12 per month or $144 per year and one-time lifetime options at $399 and $699.
QuillBot sits at the low end, with a free tier and a Premium plan listed at $4.17/mo on an annual basis. Same category, same basic job — helping you write better — but three very different price points.
The mechanism behind that spread is packaging. Writing assistants sell you a bundle of features, and each vendor bundles differently. Grammarly's paid tier leans on context-aware style adjustment, which means it changes its suggestions based on whether you're writing an academic paper, a business memo, or an email, plus logic structure optimization and a feature called Smart Drafts.
ProWritingAid splits its own audience in two: a Premium tier aimed at heavy users who want the full report suite, and a Premium Pro tier that costs less per month but is positioned differently. QuillBot's lower entry price reflects a narrower focus — paraphrasing and rewriting rather than a full editing suite.
So when you compare a $12 plan to a $30 plan, you're not comparing the same product at two prices. You're comparing two different feature bundles that happen to share a category label.
A concrete example makes this clearer. Say you write roughly ten long documents a month — client proposals, blog drafts, internal reports. On Grammarly Pro at $12/mo, you'd pay about $144 over a year under the listed monthly rate.
On ProWritingAid's Premium tier at $30/mo, the same year runs $360. But if your actual need is rewriting sentences you've already written, QuillBot's Premium at $4.17/mo annualized covers that job for far less, and its free tier may cover light use entirely. The lesson: match the tool to the task before you match it to a budget.
A writer who only ever rephrases paragraphs is overpaying badly on a $30/mo plan built for structural editing and long-form reports.
Here's where this advice breaks down. Monthly prices are not the real cost if you cancel early or pay annually and stop using the tool — annual plans usually lock you in, and the effective monthly rate only holds if you stay the full term. Lifetime deals look attractive on paper, but they only pay off if the vendor keeps updating the product for years, and software companies change ownership and priorities all the time.
Also worth knowing: these prices are snapshots. Our database records pricing and capability at verification time, and the most recent verification date is 2026-09-18. Vendors reprice, rename tiers, and move features between plans constantly, so treat any figure here as a starting point and confirm on the vendor's own page before you enter a card number.
Editorial ratings in our database — 4.5/5 for Grammarly, 4.5/5 for QuillBot, 4.4/5 for ProWritingAid — tell you how reviewers scored the products overall, not which one is cheapest for your specific job. If you want to see how free tiers fit into this picture, our breakdown of what's the best AI writing helper free option in 2026, and where does it actually stop being free? walks through where the free versions run out.
The short version: cheaper is not automatically better, and expensive is not automatically complete.