From AppleInsider's "Counterfeit iPhone trafficking scheme lands Chinese national in US federal prison":
Earlier this year, [Chinese national Quan] Jiang and former Oregon State University engineering student Yangyang Zhou were fingered by federal agents investigating a counterfeiting scheme involving Apple's hardware warranty policies. Both Jiang and Zhou carried out the illicit plan while in the U.S. on student visas.
Between January 2016 and February 2018, Jiang would regularly receive inoperable counterfeit iPhones — 20 and 30 at a time — from connections in Hong Kong and send the hardware to Apple, or carry it in to a brick-and-mortar store, for warranty replacement. Genuine articles were sent back to China for subsequent resale. Profits gleaned by the operation delivered to Jiang's mother, who deposited the funds into Jiang's Chinese bank account, the release said...
In all, Jiang imported more than 2,000 counterfeit iPhones during the two-year span, some 1,500 of which were traded in for replacements that carried a value of approximately $600 apiece.
My take: I can't believe it took Apple 1,500 dead phones to catch on.