Or think about it this way: It is a medium to high risk investment that pays 23% interest monthly. (at 0.07/GH and today's difficulty). Slightly better if you reinvest (compound) that interest by buying additional GHS on a regular basis with your interest. Obviously the "interest" will continue declining as difficulty increases which is why over a long period of time the average returns are going to be worse because the cost/GHS will continue to decrease in line with the "interest".
Don't think of it as buying mining power but rather from the investment/returns perspective and it makes a lot more sense.
I've seen posts where people say the GHS price should be 0.03. If someone was offering you an investment that made better than 10%/week and was backed, at least somewhat, by a company rather than some guy with a hammer that would break kneecaps of debtors if they didn't pay that would be pretty popular, hence the current cost.
This is how I think of it. Instead of coins sitting in a wallet, coins at CEX are generating a slight income. And if you want to trade periodically, you can make some profits that way too.
You are not getting 23% monthly. Your return drops significantly every 12 (or less) days.
You write as if you expect to get all of your initial investment back, but you won't. The price of 1 GH/s drops faster(on average) than the amount you receive as income. The price has dropped 25% in the last month, so even your exaggerated 23% was not enough to break even.
There is simply no way to make a profit at the current price. Since you lose money every time you buy cex.io, you are compounding your
losses when you reinvest.
The price should be around 0.03 BTC because that is the total amount of income you will receive from 1 GH/s. Why pay 0.07 when you are only going to get back 0.03?
You can potentially make profits by trading, but trading is going to lose money on average because the price is dropping. For every trader that makes money there will at least one trader that loses money.
I urge the two of you to make a serious effort to determine the total income you will receive from 1 GH/s and then justify paying the current price for that income.