Its easy to determine if a giveaway is legit or not. If the giveaway asking to transfer a money before participating then its abvious scam attempt .
Another things is if a giveaway is giving a high return from the asked amount you need to deposit then its the same.
This kind of scheme is not only happening in twitter its also use in other social media such as facebook youtube and telegram.
People are quite used to pay online for some sort of valuable service.
And I assume many of them don't see any difference between paying for netflix or for some of these "profitable" schemes