Based on the amount I will pay up to 90% face value, but I need proof of being legit cards / e-cards. I would rather pay more and be safe than otherwise. Also I'm interested in an ongoing business for buying Amazon gcs.
What proof would satisfy you? There no real way to tell wether these have been carded somewhere down the line. If you do buy these you should know the risks, but if you buy one create a new amazon account and spend them as fast as possible so you don't get burnt.