SEO vs paid search: how to split your effort between organic and paid

SEO, SEA, SEM: three acronyms, two levers

In France, “seo et sea” is searched 320 times a month and “seo ou sea” 70 times (SEA is the French shorthand for paid search). Both describe ways of appearing in a search engine’s results.

• SEO (search engine optimisation): the work that makes your pages appear in the organic results. You do not pay for the click; you pay for the time spent on content, technical work and measurement.
• SEA (search engine advertising), usually called paid search or PPC in English: the paid ads above or below the organic results and in Google Shopping. You pay for each click, at auction.
• SEM (search engine marketing): the two together. A useful word to remember that this is one strategy, not two competing budgets.

What a visitor really costs in each channel

The cost of a click varies enormously from one trade to another. On average in France, a click costs €30 on “serrurier” (locksmith), €8.42 on “plombier” (plumber), €13 on “expert comptable” (accountant), €3.54 on “avocat” (lawyer) and €0.27 on “coiffeur” (hairdresser). These prices are set by competitors’ bids: the more a customer is worth, the more the click costs.

In SEO, cost per visit does not exist in the strict sense: you pay for producing and improving pages, and every page that wins a search then gets visits with no bill per click. The cost per visit falls as the pages do their work. Conversely, it rises again if you stop maintaining the site and competitors overtake you.

When advertising is the right choice

Paid search has three strengths: speed, control and measurement. It is the right tool in these cases:

• Testing an offer or a price: within a few days, you know whether a page converts, before investing months of content.
• A season or an event: sales, back to school, heating season, year end. Organic search arrives too late for a three-week window.
• A new site: while the pages get indexed and ranked, advertising brings in the first customers and the first data.
• High-margin products: when a sale earns clearly more than the cost of the clicks needed to win it.

The trap: advertising towards a page that does not convert. Every flaw on the page (long checkout, hidden price, no proof) is then paid for on every click. Fix the page before buying traffic.

When organic search is the right choice

SEO wins when the horizon is long and searches are many and varied. It pays off especially on the long tail: precise searches of four words or more, too rare to justify a campaign, but very close to the purchase.

On our own sites, Google hides the query behind 93% of clicks, a sign that most visits come from rare searches; among visible queries, those of four words or more account for 39% of clicks. No ad campaign covers those thousands of variants economically; useful pages do.

• A trade where the click is expensive: every search won organically saves that price on every visit.
• A broad catalogue: hundreds of products or services, each with its own searches.
• A stable business: today’s work still pays off a year from now.
• A presence in AI assistants’ answers: they cite pages that rank well, not ads.

Combine the two without paying twice

The right split is not a fixed percentage. It is a loop where each channel feeds the other:

1. 1
   Test with paid: a small campaign on a few precise searches tells you which pages and which offers convert.
2. 2
   Build organically: the searches that convert become carefully worked, sourced, interlinked pages.
3. 3
   Cut advertising where organic wins: when a page reaches the top for a search, the campaign on that search can often come down. Check over a few weeks that total sales do not drop.
4. 4
   Keep advertising where organic cannot go: searches dominated by platforms, new products, short seasons.
5. 5
   Do not forget Bing: Microsoft Ads and Bing Webmaster Tools open up an audience that Google does not cover.

Measure both channels by the same rule

To compare, bring everything back to the same question: what does a sale or an enquiry cost, and what does it bring in? In paid search, the cost is the ad spend; in SEO, it is the time or the service spent on content and technical work, spread over the sales it brings. In both cases, measure conversions in Google Analytics 4 with the same events, and read Google Search Console for organic searches.

One last point of method: the two channels sometimes cannibalise each other. An ad on your own brand name captures clicks that would have come for free through organic search. Test it by switching it off for a few weeks and see whether total sales move.