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Paid ads: what you are actually buying

How paid ads are priced, who carries the risk in each pricing model, and how to buy advertising with a cost you can put in a budget beforehand.

"Paid ads" covers everything from a banner on a local news site to a video in a social feed, and the phrase hides the only question that matters when you are spending your own money: what, exactly, is being sold to you? There are really only two answers. You are either buying attention — a quantity of impressions or clicks, gathered from an audience someone else assembled — or you are buying space: a defined position on a defined page for a defined period. Almost every difference in how advertising is priced, budgeted and reported follows from which of the two you bought.

An auction settles at a price the buyer only learns afterwards, next to a listed daily rate agreed before the ad runs BOUGHT AT AUCTION SEALED BIDS PRICE KNOWN AFTER THE IMPRESSION IS SOLD BOUGHT AT A LISTED RATE $6.00 PER DAY PRICE KNOWN BEFORE ANYTHING IS SPENT
The same money buys two different things. On the left, a price discovered after the impression is sold. On the right, a rate agreed before anything runs.

The four ways paid ads are priced

Cost per mille (CPM) charges for a thousand impressions. You are buying volume, and whether that volume is worth anything depends entirely on who was in it. Cost per click (CPC) charges only when someone acts, which sounds safer and shifts the risk to the seller — who then prices that risk back in. Cost per acquisition (CPA) goes further and charges per sale or sign-up; the seller carries the most risk, and the price reflects it. Flat rate — sometimes called sponsorship or direct buying — charges for a period of display: a day, a week, a month.

The first three are almost always settled by auction. That is the part worth understanding, because it means the number you pay is an outcome, not a decision. You set a maximum, an auction runs, and the price emerges from what everyone else bid for the same attention. You find out what advertising cost you after it has been bought.

A flat rate inverts that. The number is agreed in advance, by the person selling the space, and it does not move because a bigger advertiser turned up that week.

Why the pricing model decides who carries the risk

Auction pricing is efficient in the economist's sense: the space goes to whoever values it most. It is also, for a small advertiser, a permanent negotiation against parties with more data and more money. If a national retailer decides your audience is interesting this month, your costs move and nothing about your business changed.

Buying a period of display removes that. A day costs what the page's owner said a day costs. If the rate is wrong for you, you do not buy it — but you know that before you commit rather than after the invoice.

Daily spend on an auction-priced campaign varying day to day, against a flat agreed daily rate SPEND PER DAY, ONE MONTH SET BY AN AUCTION SET BY YOU THE JAGGED LINE IS NOT DEARER BY DEFINITION. IT IS THE ONE YOU CANNOT PUT IN A BUDGET BEFORE THE MONTH BEGINS.
Daily spend under an auction, against a rate agreed in advance. The difference is not the amount. It is which one you could have written into a budget last month.

What a small advertiser should actually look for

How Perch prices a paid ad

Perch sells the second thing: space, by the day, on a named site. The site's owner sets the daily rate, publishes it on the sign-up page, and that is the price. There is no auction unless the space is already full, and even then the mechanism is a queue rather than a bidding war over a running advertiser — nobody who is live is ever displaced by a higher bid. A daily rate multiplied by the days you want is the whole calculation.

Two consequences follow. For an advertiser, the cost of a month is known before the month starts. For a site owner, the income from a filled slot is known too, which is what makes it possible to monetise your website without waiting to be told afterwards what your own audience was worth. A 25% service fee comes out of each payment to cover card processing, payouts, hosting and support; it is shown on screen before anyone agrees to anything.

If you own the site, the practical step is to create an ad space, set a rate you would be happy to receive, and let the slot itself invite the buyer. If you are buying, read ads for small business next, which is about choosing where to put a small budget.

None of this makes flat-rate buying automatically better. A national campaign that needs ten million impressions cannot be assembled a day at a time from individual sites, and should not be. But most people asking what paid ads cost are not running a national campaign. They are trying to reach a few thousand relevant people without signing anything, and for that, a listed price on a page they can read is a better instrument than an auction.

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