Constrained supply keeps iPhone 6 Plus resale prices at 124% of retail price

Used and resold iPhone 6 Plus units are still selling at above-cost on sites like eBay, as Apple continues to struggle to keep up with overwhelming demand for its new jumbo-sized 5.5-inch iPhone.

Analyst Gene Munster and his team at Piper Jaffray have been tracking iPhone resale prices through eBay auctions and Taobao prices. Every week, they look at the last 50 phones sold of each model to determine a fair value.

Munster found that a full 42 days after launch, the iPhone 6 Plus was still selling at 124 percent of its suggested retail price. That's better than the iPhone 5s performed a year ago, when it sold at 119 percent of value 42 days after launch.

The data suggests that Apple has largely caught up with demand for the iPhone 6, with resale values dropping from 115 percent of retail price a week after launch, to 94 percent 42 days after the handset debuted.

Apple's flagship iPhone models also hold their value better than competing smartphones from Samsung: Piper Jaffray's research shows that the Galaxy S5 was worth just 81 percent of its retail price after 42 days, while the Galaxy Note III plummeted to 67 percent.

To Munster, the resale values suggest that the so-called "bendgate" controversy has been a non-factor with consumers looking to buy the iPhone 6 Plus. He also noted that used iPhone 5s and iPhone 5c pricing has declined more sharply following the debut of the iPhone 6 series than the iPhone 5 did a year ago.

"We view this greater decline to be expected given this year's 6 and 6+ hardware improvements are more substantial, which we believe makes last year's model slightly less desirable compared to an S upgrade cycle," Munster wrote.

Piper Jaffray has maintained its price target of $120 with an "overweight" rating on shares of AAPL.