CNN and other cable news channels carried Donald Trump's press conference live on Monday.

You've surely heard the complaint/boast that the news media are Donald Trump's biggest boosters. The Republican presidential front-runner gets more coverage (like, way more coverage) than any other candidate — a source of consternation for some and pride for the man himself, who brags about getting "so much free advertising."

But is "free advertising" really a fair way to describe all the attention? Optimus Consulting, a Republican data analytics firm that has conducted research for a super PAC backing Marco Rubio, contends that the answer is yes.

Actually, Optimus contends that $2.8 million worth of advertising — and in-kind "donation," if you will — is really more accurate. And that's just for one day.

The firm on Thursday published its analysis of how Fox News, CNN and MSNBC covered a Trump press conference on Monday. Optimus assigned a dollar value to the airtime. Here's how:

We can get a good approximation for the value of this time by looking at what it would cost to have bought comparable airtime on the same channel. For example, buying a 30-second ad spot on Fox News, nationwide, in the 2 p.m. ET time block would cost around $10,000. So if you wanted a minute of time, you’d have to pay $20,000. If a campaign wanted to buy 20 minutes of time (like Trump received during his press conference), the cost would be $400,000. Using this logic, we conclude that Trump was given airtime to push his message that was worth $1.01 million dollars during his press conference alone. ...

Post-coverage took many forms: quick recaps of the conference from reporters, soundbites from Trump’s major quotes, panel discussions of the conference; CNN even had Mr. Trump call-in live to discuss his 40-minute press conference. These were panels that were not discussing if Cruz or Bush or Kasich or Rubio were surging; they were instead, once again, talking about Trump and his main messaging points. In any campaign, the most expensive costs are TV ads. As this final chart below illustrates, Optimus calculates that the free exposure Mr. Trump received from cable television on Monday alone is the equivalent of $2.8 million dollars in free TV media.

Optimus is not the first to attempt this kind of calculation. Media Matters for America, the left-leaning press watchdog whose founder, David Brock, also heads a super PAC supporting Hillary Clinton, estimated that Fox News alone gave Trump almost $30 million of free airtime last year. That figure was based on Trump's interview time on the network and the cost of buying equivalent advertising time.

The problem with these analyses, though, is that they equate interviews and panel discussions with ads. That's silly; they're just not the same.

An ad is pure, positive spin. You make yourself look as good as possible (or your opponents as bad as possible), and what you're really paying for is the ability to broadcast your message without a filter or a fact-checker. Interviewers and panelists push back (or at least should). They ask tough questions and call you out when your claims are exaggerated or misleading or completely untrue. They don't always perform these functions perfectly, of course, and you still have an opportunity to reach your audience, but you give up the control that you buy in a commercial. There's a big difference.

What is closer to a free ad, however, is a prolonged, live telecast of a press conference — which is what Trump got from all three major cable news channels on Monday. He's the leading Republican candidate for president; what he says certainly has news value. But giving him a 20- or 40-minute block to do his thing, without anyone to challenge a word he says, affords many of the same benefits as an ad.

It doesn't seem fair to say, as Optimus did, that cable news essentially donated $2.8 million to Trump on Monday. But on the underlying issue of free promotional airtime, the firm does have a point.