Apple, which purchases used iPhones as part of its , has kept its 16GB iPhone 4S appraisal steady at $285 for the last seven days.

eBay's Instant Sale website quoted the same $300 it did a week ago.

"We've seen a drop in [quote values] of between 5% and 10% across all iPhone models since the announcement," said Anthony Scarsella, chief gadget officer at Gazelle, referring to the iPhone 5 event Apple hosted Wednesday in San Francisco.

The decline was not unexpected: Prices paid by trade-in vendors have fallen after each previous iPhone or iPad launch event.

, and announced price cuts for 2010's iPhone 4 and last year's iPhone 4S. Apple will continue to sell the last two iPhone generations: A 16GB iPhone 4S now costs $99, or a 50% reduction from Tuesday, while an 8GB iPhone 4 is free.