They probably can do that but they'll need to be experienced with Minecraft anti cheats to find exploits that make certain modules (speed, fly...) bypass.
You aren't allowed to sell it, your account will be locked.
If they aren't scamming, they usually just rat people with Vape, get their account, resell it and when the account gets locked/the original owner gets access back they'll just block you.
If you use any creator discount code (eg. rain) you'll get 30% of on all Vape products.
Additionally, Vape Lite lifetime is purchasable again (sorry if it returned before the black Friday sale, I haven't been keeping up with stuff like that).