When you want to buy a key make it as hard as possible for them that they don't scam you. Here are some tips as there are a lot of scamming going on.
1. Ask for a screenshot of the beta access with the skype chat next to it.
2. Ask them to stream their screen of the beta key invite with your skype chat next to it.
3. Be extra cautios with accounts that are just created as they got a very high chance of scamming.
4. When leaving your skype in the thread to be contacted. Ask who the person on ownedcore is and have them message you ingame to verify it's them and not someone else and add step 1 to it.
Overall don't make it easy for them. As i made few fake accounts to catch scammers and left my fake skype behind. I got contacted by 8 guys pretending to be that person. One guy even went so far to contact op and let op do what i asked the scammer to do. And the real op thought he was contacting me while the scammer was in between us. Making it look like we were talking with each other.