Less than $20 for a sweater? In most cases, that’s not just hot, it’s highly flammable.

As in “100 percent acrylic” flammable.

But Sarah Jessica Parker’s first fall fashion collection under her new Bitten label, exclusively at Steve & Barry’s stores, has managed to produce cashmere-blend cardigans at that bargain price. Wool coats, tailored suit pieces and little black dresses punctuate a staggering breadth of more than 500 women’s items.

Not one of the price tags exceeds $19.98.

This latest evolution in the cheap-chic revolution challenges the typical word associations, such as “disposable fashion” and “Target.”

Bitten’s freshness is one reason that more than 1,000 women, and a few men, mobbed Parker’s appearance at the Steve & Barry’s store in Mt. Prospect, Ill., earlier this month.

A Marc Jacobs tote on one arm and a Bitten bag in the other, Rinoula Litos, 21, emerged from the Parker appearance in Mt. Prospect with an autographed photo as well as jeans, three T-shirts, a hoodie and pajama pants.

The clothing from Parker’s new Bitten line had cost about $60 total, said Litos, her wrist dangling two gold-finish heart bracelets, a previous Bitten purchase.

“It’s cheap,” said Litos, a DePaul University student. “But it’s a good cheap.”

Parker reached a similar conclusion after the Steve & Barry’s chain approached her about creating a line that would be its major entry into the women’s market. Retaining Steve & Barry’s $20-and-under pricing and produced with the help of a design team, the line would uphold the mantra: “Fashion is not a luxury, it’s a right.”

Parker says she loves the company.

“And I love that there was an opportunity to address a lot of women’s needs that are marginalized sometimes in the world of fashion,” she said.

Not just trafficking in teeny juniors sizes, Bitten goes up to XXL in tops, size 22 in bottoms and size 11 in footwear.

Many Bitten garments are made in China, but are done so under an “incredibly strict fair-labor policy,” said Steve & Barry’s partnership chief Howard Schacter.

The chain maintains its prices by skipping expensive ad campaigns, but also by folding clothing in a less labor-intensive way and sending trucks out only when they’re full. Other cost efficiencies, Schacter said, include “staying in Howard Johnsons when I have meetings in L.A.”