Fox News’ John Roberts on Thursday hit Commerce Secretary Howard Lutnick with a brutal lesson in “reality” versus “perception” after Donald Trump repeated his lie about cutting prescription drug prices during his primetime address.

In a falsehood-filled, shouty speech from the White House, the president pulled a familiar lie from out of his hat, declaring that drug costs are “400, 500 and even 600%” lower.

Trump has paraded the implausible claim around in recent months, baffling critics. Back in July, he vowed to force pharmaceutical companies to drop drug prices by up to 1,500% and “numbers that are not even thought to be achievable.”

Roberts pointed out the obvious about Trump’s “mathematically impossible” claim during Lutnick’s appearance on Fox News’ “America Reports.”

“Well, if you cut something by 100%, the cost goes down to zero. If you cut it by four, five, or 600%, the drug companies are actually paying you to take their products,” explained the host as Lutnick cracked a smile and chuckled.

“So it raises the question: How much of last night’s speech was hyperbole and how much was fact?”

Reducing the price of a drug by 100% would make it free. Any further decrease in percentage would mean companies would be paying people to take them.

Lutnick tried to put on his math hat.

“What he’s saying is if a drug was $100 and you bring the drug down to $13, right? If you’re looking at it from $13, it’s down seven times!” Lutnick claimed.

“It’s not 600%,” Roberts interjected.

“Well, it’s 700% higher price before, it’s down 700% now, right?” continued Lutnick as he tried to explain Trumpspeak.

“So $13 would have to go up 700% to get back to the old one. So it all depends on when you look at it. You could say it’s down 87% or you could say it would have to go up 700% to be the same one, so it just depends on when you look at it.”

Lutnick marched on, “But basically what he’s saying, and we all know what he’s saying, is we are hammering the price of drugs down…”