This is where author Tonello comes in. Bringing Home the Birkin relates how he discovers the rabid nature of Birkin

This is where author Tonello comes in. Bringing Home the Birkin relates how he discovers the rabid nature of Birkin collectors after selling his own belongings on eBay as a means to make money to remain in his adopted city of Barcelona. Running low on cash, and with no prospects for local employment, he decided to sell the one Hermes item he owns-a cashmere scarf-on eBay. A bidding war broke out for the scarf, and Tonello pocketed a tidy profit. After that, he began receiving daily email "wish lists" for Hermes items from potential customers, including many fervent pleas for the elusive Birkin bag.
At the time, Michael Tonello was no stranger to the luxury market. However, he was unfamiliar with the rumored Hermes sales technique, which excludes buyers not just by economics, but by refusing to sell certain items, most notably Birkin bags, to customers who simply wander into Hermes stores off the street.