Police said in a statement the 20-year-old Briton had arrived in Milan on July 10 for an alleged photo shooting arranged through her agent.
The model, who has not been named, was reportedly sent by her United Kingdom agent to Milan for a photo shoot on July 11 and when she arrived at the studio near the city's central railway station she was anaesthetised with the powerful drug Ketamine injected into her arm.
Her kidnapper reportedly demanded €300,000 off her agent in the United Kingdom to prevent her "sale" online.
A UK-based modelling agency sent the woman to the "photoshoot", and once she arrived, was promptly injected with the powerful anaesthesia Ketamine, handcuffed, and stuffed into a suitcase with a pillow case over her head, according to the report.
The websites for the auctions included a description of the victim and a starting price but police said it was still unclear whether the suspect had made them up.
The paper says she was released on July 17 because her alleged abductor discovered she had a young child and considered her unsuitable for sex trafficking.
He has been charged with kidnapping for the purposes of extortion.
The woman, who has not been named, was allegedly kidnapped by two men on 11 July as she turned up for a fake photo shoot.
Officers went through Herba's phone and computer and said they found photos of the woman and material stating she was for sale, while hair from both the model and Herba was found in the boot of his vehicle.
Italian police said they are working with officials in Britain and Poland as they continue to investigate.
The woman, whose identity has not been revealed, was held prisoner for a week after being drugged, authorities said.