In short: if you pay the $24-30 now you will get the full PUBG game when it releases as a finished product.
Long: it should be like Ark. You pay ~$30 now to get a game that is not finished. There is a risk that the game will never "finish" and be left as it is.
You still get the full game if there is a final released product (at say $60). Assuming the game is completed, you pay $30 for a $60 game and get to play it during its beta.
I brought up Ark because it's an example of a game going out in preview, players paying a lesser amount to play the "beta", and then finally releasing as a $60 product. Those that paid for a preview copy still got the full $60 game when it released. However, the developers ALSO released an expansion pack Scorched Earth (in preview mode) BEFORE Ark was released. Scorched Earth was outside the original Ark preview game and had to be purchased separately.