Like many other online trade-in programs, Quick Sale lets you get an estimated offer for your phone after you answer a few questions through the website. The price will be based on the condition, storage capacity, color and brand. Once that's all been determined, eBay will provide a free shipping label that you can use to send your handset in. The sale will go through the eBay Valet service that sells your stuff on your behalf.
After the company receives your pre-loved device, it will confirm the condition and pay you. The whole process will take about 7 to 10 business days after you send in your phone.
A quick check showed that Quick Sale offered me $311.50 for a space gray 128GB iPhone 6s in good condition, while Gazelle only suggested $230 for the same specs. Glyde, however, will give me about $361 if I throw in a charger.
While there is no fee for selling through Quick Sale, and you'll get just what the company offers you answer the website's questions, you might still be able to fetch a higher price if you set up an auction yourself. But considering what other buyback programs are offering, the eBay service appears to be pretty competitive, at least on first glance.