Half value = red flag.
But there are ways to earn 5 dollar amazon cards for free via the bing search engine.
I suspect someone has 1000 emails and with scrypt coding could earn 1000 x 5 = 5000 in cards a month.
I earn 1 every 22-28 days as does my wife.
How does it work and what do you need to do? Are you receiving points just for using bing and google?
I would never purchase a gift card from a seller advertising that he has a huge amount or that he can get any amount anytime. Those are hardly legit.