The fact that you don’t actually buy GHS at a fixed price, but instead you can purchase hashrate at the current market price is both a good and a bad thing. Due to the fact that there is an exchange available you need to trade BTC or NMC for GHS in order to get some hasrate to mine for you, so you can expect the price you will have to pay for 1 GHS to be 2-3 times higher than what you would pay for a physical Bitcoin ASIC. The good thing with cloud mining at CEX.io is that you can easily and quickly sell your hashrate at the exchange at any time. The bad thing is that there is a very high chance that in a few days or weeks of time the exchange rate per GHS will most likely be lower than the rate at you purchased. This is happening because of the constantly increasing difficulty of the Bitcoin network, and as a result the rate at which your cloud hashrate is mining coins for you will also drop in time. This makes it not worthwhile to invest in GHS on the long run expecting that you will end up with profit from what you have mined with the purchased hasrate after you sell the gigahashes you purchased on the exchange in a while.