why dont you just sell it on those giftcard websites? and then buy btc?
selling it for paypal , and exchange the pp to btc... i will lost more than 25%...
I don't think you will be able to get 85% for a gift card
Even if you are trusted, this is the upper range that people will get for them. If you are not trusted then you will get much less because of the high risk of having the gift card reversed off your amazon account.
It is my understanding that gift cards tend to sell for much more via those trading sites because your identity is tied to the trade and they have ways to reverse the payment they send you if there is an issue with the card you sell