For Charles Gorra, whose company Rebag has bought and sold luxury handbags since 2014, the competition isn't Hermès or Louis Vuitton. "We like to say we don't compete against this or that company, but we compete against idleness," Gorra said on the Glossy Podcast.

His estimate is that nine out of 10 "luxury owners" have never sold those items and that most of his customers (on the selling end) are doing so for the first time.

It helps that Rebag buys such pieces upfront, in its nine physical locations in Los Angeles, New York State and Miami. Thirty stores is the "medium-term goal" for the company, said Gorra. Handbag sales, however, are mostly done online, with only 20-30% sold in store. "We're still largely a digital company," Gorra said.

Accordingly, Gorra thinks Instagram Checkout -- which is still in beta -- could be "game-changing" for e-commerce in general. And last year Rebag launched Clair, or Comprehensive Luxury Appraisal Index for Resale, a freely-available tool for appraising bags at a distance.

"Literally, it's three or five clicks, and we tell you right there: 'This is how much we pay,'" Gorra said. He previously told Glossy that unlike sneakers, designer handbags tend not to have product codes or SKU numbers, which come into play in the authorization process. Clair is Rebag's way of bringing some standardization to the market.

Gorra talked about Rebag's typical customer, his stores' experiential fixtures and the item appraisal tool that Rebag launched last year.