"Them may be legits" for about a week or 3 or 4 then the Amazon Police will find them aren't legits then who will them come after?  Not you.  There are a lot of places you can sell "legit" Amazon cards for 90%+ of value so just the fact you chose to sell them here makes it very suspicious.  If you were smart you would have said you have 2 or 3 to sell not 300.