where it say that is monthly? the price is to expensive for beginners, and 10 sol will give you nothing, so you are fo rced to invest quite big at launch which is not convenient and too risky, they should do short terms instead of those long term if your months times are correct
Where did I say monthly? 
Genesis-Mining.com is yearly (i.e. one year) and Zcash-Miner.com is quarterly (i.e. three months).