It’s not just that the investigation by special counsel Robert S. Mueller III is, in President Trump’s estimation, a biased partisan “witch hunt." No, that’s just one small aspect of why Trump is frustrated by Mueller’s work.

There’s Trump’s worry that the probe “endangers our country,” as he told reporters on Air Force One last week. Why? Because it is “hard for us to deal with other countries” because of it.

And then there’s the cost. In June, he took issue with the cost as reported by Mueller’s team.

That figure came from documents filed by Mueller’s team with the Department of Justice.

When former campaign adviser George Papadopoulos was sentenced to two weeks in prison last week for lying to federal investigators, Trump compared his sentence to a figure of $28 million, presumably also a reference to the probe’s cost.

Where that number came from, though, isn’t clear. If we assume the same cost-per-day for the investigation that was reported through March of this year, the probe has so far cost the government about $26 million. That’s the $17 million through March and another $9 million since.

But here’s the thing, pointed out by journalist Marcy Wheeler on her personal site: The Mueller probe may have just paid for itself.

Why? Because part of the plea agreement reached between Mueller and former Trump campaign chairman Paul Manafort includes forfeiture of certain property to the government. While it’s not clear how much value will be extracted from that forfeiture, there’s reason to think that it could more than pay for what Mueller has incurred so far.

For example, there are five properties that are being forfeited, as follows:

(The document filed with the court on Friday morning identified four properties being forfeited. A later document detailing the plea agreement identified the Baxter Street and Trump Tower properties as being substituted in for a property in Arlington, Va., and for a Charles Schwab brokerage account.)

The combined value of those properties, according to estimates at and assigning the 2006 sale price to his Trump Tower property, is about $22.2 million. If those were sold at the values identified above and the money returned to the government, that alone nearly covers our estimated costs of the investigation to date.

Jennifer Rodgers, executive director of the Center for the Advancement of Public Integrity at Columbia Law School, explained in a phone call to The Washington Post that unless Manafort owns the properties outright — that is, without a mortgage or co-owner — there will be an agreement on how to split assets from a sale.

Former Trump campaign chairman Paul Manafort pleaded guilty to two charges on Sept. 14, and will cooperate with special counsel Robert Mueller's investigation. (Jenny Starrs/The Washington Post)

“Sometimes if it’s joint ownership, you do have to go through a process with the other owners, with the other parties,” Rodgers said. “The government will do that as part of the forfeiture process. You can seize them, but seizing them doesn’t mean it’s all said and done. ... They do have to account for any other owners.”

If there’s a mortgage, “the bank is not going to be out because he is a criminal,” she said.

Those properties also aren’t the only items of value being forfeited. Manafort also has to give up his life-insurance policy. It’s not clear what the value of the policy is, but when he was first indicted he presented the court with a life-insurance policy or policies that he valued at about $4.5 million. Prosecutors were skeptical that the policies were worth that much.

Then there are three bank accounts that Manafort is also forfeiting. None of the values of those accounts is clear.

But one, Wheeler notes, may be tied to a $16 million loan Manafort got from Federal Savings Bank. A bank executive testified in Manafort’s Virginia trial that the institution had written off $11.8 million it was still owed; it’s not clear whether that value is tied up in property or in an account.

We’re left with a broad range, then. The government’s seizures from Manafort could be worth about $42 million, including the upper estimates of just the properties, Federal Savings Bank loan and insurance policies. And that doesn’t include the other accounts, which might contain some portion of the $30 million that Wheeler points to as having been identified by the government as ill-gotten gains. That’s enough to pay for the Mueller probe for some time to come.

What was seized could also be, and probably is, a much smaller amount. At the time that Manafort was first indicted, he claimed to be worth $28 million. That presumably includes the value of his properties, which would suggest very little cash on hand — even before he spent months defending himself in court. That claim, though, is worth taking with a grain of salt. We know that Manafort’s past assertions have proved to be inaccurate, to put it mildly.

The plea agreement spells out that there is no restitution mandated of Manafort. In other words, what the government gets from the bank accounts, insurance policy and sale of the properties is the extent of its compensation, that $30 million notwithstanding. Former assistant U.S. attorney Mimi Rocah, who spoke by phone with The Post, indicated that the lack of mandated restitution was unusual. Because the agreement is essentially a contract between Manafort and the government, though, that was probably a subject of the negotiations.

There have been rumors for some time that Trump might pardon Manafort. If he does so, both Rocah and Rodgers suggested, the government will probably get to keep what’s been seized anyway.

The plea agreement stipulates that Manafort “agrees to forfeit criminally and civilly the following properties.” That “civilly” is important.

“Civil forfeiture is separate, and he stipulated to it, so it’s going to be done now,” Rodgers said. “A pardon wouldn’t affect that.”

“I would think it would be very hard for him to get his property back,” Rocah said. But, she added, “that doesn’t mean he wouldn’t try to pardon him.”

After all, Trump does have other concerns related to Manafort that a pardon might aid.