NEW YORK ( TheStreet) - Apple's ( AAPL) iPad, which competes with Amazon's Kindle and Barnes & Noble's ( BKS) Nook in the e-reader market, is continuing to see substantial growth in sales, and we expect this trend to continue.The tablet PC market has grown exponentially with leading PC makers like Dell ( DELL) and HP ( HPQ) introducing their versions of tablets like the Streak and Slate, respectively, in order to compete with the iPad. Though we expect Apple to face competition from a flurry of tablet devices, many of which are being showcased the Las Vegas Consumer Electronics Show (CES) taking place this week, we believe that Apple will continue to dominate the tablet device market for the foreseeable future. While we expect iPad unit sales will touch close to 30 million by 2013, Trefis members predict sales will reach almost 40 million. Though this is well above our current estimates, it has a limited impact on the stock right now, given the iPad accounts for around 7% of our estimate price estimate. We currently have a Trefis price estimate of $418 for Apple's stock, about 27% above the current market price of $330. Apple announced that within 28 days since the launch of the iPad on April 3, 2010, the company had sales of 1 million iPads, and sales of more than 12 million apps from the App Store and over 1.5 million ebooks from the new iBookstore. This milestone was achieved in less than half the time it took to the iPhone to achieve. According to eMarketer estimates, iPad sales will cross 19 million units in 2011 and 30 million units in 2012. It also predicts that the tablet market will diversify further and that iPad's share of the tablet market will reduce from 88% currently to 69% in 2012. However it will still retain its high market share. We expect the average iPad pricing to decline from $640 currently to around $540 by 2013. Lower prices should increase demand for iPad and hence boost sales. The company already has basic features like Web browsing, reading and sending emails, sharing photos. If Apple is able to add more features like a camera, OLED display and a removable battery, this will give more traction to sales.