The inaugural report shared with AppleInsider compared U.S. eBay auction prices for the iPhone 5, iPhone 4S, iPhone 4, Galaxy S III and Galaxy Note II , a method that looks to determine the current consumer climate for Apple's handset.
According to analyst Gene Munster, the index is "a pulse on what consumers are willing to pay for unsubsidized phones in the US.
"The key takeaway from 8 weeks of data is that the iPhone is holding slightly more of its value compared to the top two Galaxy phones," Munster wrote.
Despite being 46 percent more expensive than the Galaxy S III, Apple's latest iPhone 5 shed 11.2 percent of its value compared to 13.7 percent for the Samsung smartphone.
Interestingly, the highest performing handset in the focused study was the iPhone 4S, which managed to lose only 7 percent of its value over the two month period. Coming in second was the iPhone 4, which lost 8.8 percent, followed by the iPhone 5. Median iPhone 4S pricing wen from $349 in March to $312 in May, while the iPhone 5 fell to $465 from $535 over the same period.
Samsung's Galaxy S III and Galaxy Note II were the biggest losers, dropping 13.7 percent and 15 percent, respectively. Median pricing for the S III fell to $320 from $360 over the eight weeks, and the Note II moved from $550 ro $444.
As noted in the report, decreased auction pricing for the iPhone would suggest existing owners are expecting a new version, and are flooding the market by selling off their handsets in preparation of a next-gen model. A dip in value could also point to a shift in preference toward the Galaxy lineup.
While a spike in sales has yet to be seen, resale prices are expected to drop as Apple's usual fall iPhone refresh cycle approaches.
"We believe that the iPhone aftermarket price should continue to decrease as we approach an iPhone 5S launch which we expect at the end of the month of September," Munster said.
As for the study's methodology, Piper Jaffray monitored eBay auction prices since March 15, taking weekly looks at the last 50 phones sold to determine a "fair value" for each device.