The number of people selling their old tablets increases as the media event for Apple's iPad Mini. People are starting to sell their old tablets in various websites such as Gazelle.

Chief gadget officer of Gazelle Anthony Scarsella said that tablet trade-in volume was up 80% in the previous 30 days. "Volumes started going up in mid-September, when they doubled in one day. Since then, they've stayed pretty stable," said Scarsella.

"Since the October 23 event invites went out last week, we've seen a significant increase in the number of iPad trade-ins," he said in a follow-up email today. During the week of Oct. 15, quote requests were up 320% over the week before, Scarsella added.

Unlike the early interest, the most recent has been more about selling the newest iPad, which jumped 520% in quote volume.

Perhaps most interestingly, the number of iPad 3s traded in has increased tremendously, accounting for more than 40% of total trade-ins in the last week.

Tech giant Apple announced that it will hold a media event on October 23 and hinted about the release of an iPad Mini.

The company did not specify what it has planned for the media event. Its invitation said only that it has "a little more to show you." However, speculations claimed that the firm will show off the long-awaited iPad Mini.

The iPad Mini is reported to be the new little iPad will feature a 7.85-inch IGZO display with 330 pixels/inch, 1024 x 768 resolution. It will be more affordable. It is also assumed that the new tablet will feature Apple's upcoming operating system, iO6.

Putting iOS 6 in the mini tablet will include a new, Google-free Maps app, and Passbook, and promises better Facebook integration, better maps, and better video conferences that use cellular data, according to Entrepreneur.com. It is also said to have a smaller dock connector and thinner bezel. It may also feature a music service similar to Pandora radio, WiFi, and Retina Display.

Rumors claimed that iPad Mini will cost around US$299 and US$349, which is more expensive than its rivals Google Nexus 7 and Kindle Fire HD that starts at US$199. With the aforementioned features as well as the timing, iPad Mini can be the new cash cow of Apple.