AI SEO vs. Hiring an Agency: A Cost Breakdown

Every merchant who’s looked into SEO help has had the same uncomfortable moment. You get three quotes. One agency says $800 a month, another says $3,000, a third wants $6,000, and all three describe the work in near-identical language.

Meanwhile there’s a growing pile of AI tools promising to do some version of the same thing for a fraction of that. FullSweep SEO is one of them, so treat what follows accordingly — but the comparison is worth doing honestly, because the two options aren’t substitutes and the marketing on both sides pretends they are.

What does an agency actually cost?

The published survey data disagrees with itself, which is itself informative.

Ahrefs polled 439 SEO professionals in 2026 and found the average agency retainer sits around $3,209 a month. Clutch, drawing on a much larger pool of agency reviews, lands close to that at roughly $3,199, with one-off projects averaging around $37,000. But SE Ranking surveyed 260 agencies and found that 64% charge under $1,000 a month.

Those aren’t contradictory so much as measuring different things. Averages get dragged upward by enterprise agencies billing five figures. The most common single band in the Ahrefs data is $501 to $2,000, covering about 43% of respondents.

For a small Shopify merchant, the realistic number is somewhere between $1,000 and $3,000 a month for anything with content production in it. Below that you’re generally buying monitoring and a report.

One more line item worth knowing about: GoodFirms found that among agencies raising prices in 2025–2026, a substantial share cited AEO and AI search work as the reason, often billed separately at $900 or more per month. If you want the answer-engine side covered, assume it’s an add-on.

What are you actually buying at that price?

Hours and judgment. Ahrefs’ data puts agency hourly rates near $99, with consultants higher at around $171.

Run that backward and a $2,000 retainer buys you roughly twenty hours a month across a team. That’s a strategist, a writer, maybe a technical specialist, splitting a part-time week between your store and everyone else’s.

Twenty hours is enough to do a handful of things well. It is not enough to rewrite a 1,200-product catalog. Which is why agency proposals for large stores almost always scope to a subset: the top 50 products, the main collection pages, a few blog posts a month. The long tail stays untouched, usually forever, and nobody’s being dishonest about it. There just aren’t enough hours in the retainer.

What does an AI tool actually replace?

The production, not the thinking.

The work of writing a description, a meta title, a set of alt tags, and structuring a page so it answers questions clearly — that’s high-volume, moderate-judgment work. It’s exactly what gets rationed under an hourly model, and it’s the part where software genuinely changes the arithmetic. A tool doesn’t get faster per page than a good writer. It just doesn’t stop after twenty hours.

So the honest framing isn’t “cheaper than an agency.” It’s “covers pages an agency was never going to reach.” Your 900th product was never in the retainer scope. Now it can be.

That’s the specific gap FullSweep SEO was built for: whole-store coverage across products, collections, pages and blog posts, with bulk processing doing the volume and a before/after diff on every change so you approve, edit or skip each one. Current tier pricing is at FullSweep SEO’s pricing page, where every plan is a pool of credits you spend on whatever needs the work — plus one-time credit packs if a single big sweep is all you’re after.

What does an AI tool not replace?

Four things, and being clear about them matters more than the pitch.

Strategy. Deciding which categories to compete in, what your positioning is, whether you should be fighting for a term at all. That’s a conversation with someone who understands your market.

Link acquisition. Nothing generates authoritative links for you. That’s outreach, PR, relationships, and it’s a genuine reason agencies cost what they do.

Technical diagnosis. If your site has a crawl problem, a broken canonical setup or a theme that’s mangling structured data, that’s a developer or a technical SEO. Content tooling won’t find it.

Judgment about your own products. Software works from what your store already says. If the underlying data is wrong or missing, better prose doesn’t fix it.

How should you actually compare them?

Not on monthly price, which is the comparison both sides want you to make. Compare on coverage per dollar and on what stays undone.

Ask an agency, plainly: how many pages will actually be rewritten in month one, and month six? The answer is usually smaller than the proposal implies.

Ask a tool vendor: does this touch collections and static pages, or only products? Do I see changes before they publish? Can I undo them?

Then look at what’s left over in each scenario. With an agency, it’s usually the long tail. With a tool, it’s usually strategy and links. Those gaps cost different amounts to fill.

So which one fits your store?

Rough guide, and it depends more on catalog size than on budget.

Under about 100 products with a competitive niche and a real budget, an agency probably gives you more. There’s enough retainer to cover your whole catalog and still do strategy and links, which is where the leverage is at that size.

Past a few hundred products, the math flips. No affordable retainer covers your catalog, so you’re paying premium hourly rates for partial coverage while most of your store stays as it was. Tooling handles the volume for a fraction of the cost, and any money left over goes further on a consultant for direction than on a production team.

Plenty of merchants run both, and that’s usually the sensible answer at scale: software for the sweep, a person for the questions software can’t answer.

The one option that reliably fails is the $500-a-month retainer bought in the hope it’s a cheap agency. It’s generally reporting with a bit of upkeep attached, and it produces a monthly PDF showing you the problems you already knew about.