With some US Apple stores reportedly selling out of iPhones , a wave of online entrepreneurs are cashing in, with thousands of iPhones for sale on eBay .

At around 9.30am EST today (2.30pm in the UK), unopened 8GB Apple iPhones were selling on eBay for around $750-$800 (£375-£400), compared with the $599 (£300) original retail price, reflecting the strong demand for the higher capacity version of the iPhone. According to research from investment firm Piper Jaffray , the 8GB iPhone was by far the best-seller over launch weekend.

Meanwhile on eBay, 4GB Apple iPhones were trading at around $550-$600 (£275-£300) mark. The 4GB iPhone's retail price is $499 (£250).

Reports this morning suggest that over the weekend AT&T stores sold out of iPhones, while many Apple stores have run out of iPhone stocks. Half of West Coast Apple stores sold out within the first day, according to reports.