i've been looking to invest in a antminer s9, at the moment the earning i can get from that machine is around 10$/day. but it's a litecoin miner (Antminer L3+) for the exact same price that i could earn 30$ a day from. people say that the value of bitcoin will rise like a rocket, but i dont know about litecoin.
Invest? Run the math first on bitcoinwisdom.com. Unless you have free power (and won't get into trouble drawing a kW of AC 24/7; it won't be profitable for long.
Difficulty rises and will continue to do so; until the correction comes; which- it will.
Now would be a bad time to buy a miner. I would wait for a major price correction-- even if BTC hit 10k before the correction- the money to make would be after it drops back down to 5k and the miners are all worthless; then start them up after the price rebounds.
Bitcoin mining is too hot to touch right now if you are not already heavily invested in the game.