Worried about the price of a new iPhone 6 or Galaxy Note 4? You can easily cut the price of that device by at least a third by simply trading in an old one. Many trading businesses, retailers and manufacturers will pay cash for a smartphone in good condition. Here’s how to get the best price:

Trading in a phone is as simple as getting a quote from a trading service, mailing in the device and waiting to receive the money. With the process so easy, it’s surprising that only about 20 percent of smartphone users trade in an old device when purchasing a new model. However, prospective sellers should take into consideration the highest trading prices go to devices in near-new condition. Wear and tear and significant damage can drastically reduce the value of a smartphone.

The Wall Street Journal notes smartphone traders can get the most money for their old iPhones on Amazon.com  (NASDAQ:AMZN) but would have to settle for payment in the form of an Amazon gift card -- a small vexation considering those who sell old smartphones on Amazon can get as much as $400, depending on the carrier and brand.

Other smartphone trading sites, such as Gazelle, NextWorth and Glyde, offer cash in exchange for a gently used smartphone. Though returns from these sites are not quite as high as on Amazon, consumers can easily get as much as $300 for trading an iPhone. Considering many smartphones cost $200 to $300 with a two-year contract, customers can get a new smartphone for free if they trade in an old smartphone first.

Like Amazon, retailers including Walmart (NYSE:WMT), Target (NYSE:TGT), Best Buy (NYSE:BBY) and Apple (NASDAQ:AAPL) offer gift cards in exchange for old devices. Notably, Apple offers the least money of all the exchange programs.   

As the incumbent Apple device, the iPhone 5s currently trades for the most money. Verizon customers will get the best deal, as much as $400 on Amazon, while Sprint and AT&T customers will get about $300 on Amazon, the Journal reported. T-Mobile customers should be able to get as much as $350 in cold, hard cash when trading in an iPhone 5s on Glyde.

In comparison, the current Galaxy Note 3 trades quite well on Glyde. T-Mobile customers will get the best deal on trading the Galaxy Note 3, as much as $400, while Verizon customers will get about $370, AT&T customers, about $330, and Sprint customers, about $280. Prices for the Galaxy Note 3 on Amazon are slightly lower.