It's just classified as beta now and you have to pre-order. They are doing this until the game is released on steam, sometime late january or febuary.
Pre-order prices are unkown. if you bought the original darkfall, you get the game for the price of a subscription and a month free (or as I look at it, you just pay for another month.) If you did not own the original darkfall, price is unkown but expected to be around $30 (with the first month free.)