Do prices of older iPhones decrease after the release of a new model?

Solution 1:

During the iPhone 11 announcement, Apple said they were reducing the price of the iPhone 8 to starting at $449 and the iPhone XR to starting at $599. These price changes are currently effective on Apple's website.

Historically, Apple announces new models and pricing and at the same time, refreshes their official pricing the same day as the keynote / press release. Additionally, look online and at Apple stores as they then sell (often at further discount) any now “discontinued” models in the Certified Refurbished / Clearance section:

• https://www.apple.com/shop/refurbished

Solution 2:

Apple typically announces new phone models in September. The new phone models usually take the spot at the high end of Apple’s pricing structure and the last one or two years of models slide down in price to become the “low cost” iPhone options. The pricing change occurs right as the new iPhones are announced, even if the new phones won’t ship for another month or two.

Here in 2019, Apple just announced its new phone lineup last week. iPhone 8 now sits at the bottom of the pricing structure. The price adjustments have already been made for this phone release cycle.