Even if the price of GH/s falls to zero they do not care because they charge for the maintenance costs. At some stage they will just turn off the miners but in this production cycle the old miners will be replaced by the new ones with better GH/s vs costs of electricity ratio. They can prolong this game as long as there are miners in existence and people willing to buy more hashing power at better prices. Pricewise they are fary ahead of any competition and they are selling very expensive GH/s with very expensive maintenance fees. For this money they can have cutting edge technology solar powered DC with dirt cheap miners.
That's why I think CEX is well and far from falling.
If they have solar power energy they have higher costs. To cut the maintenance fees by 50% and still make money, they would need to move in a cheaper country and really think low cost. The price per GHS would go up a lot.
For solar panels, ROI depends on how much the state is subsidizing the buying.
Solar energy is usually more expensive but if you take into account the state subsidy or special situations (you have a home away from everything), you might ROI
You are correct but maybe you can ROI if you are in the few states where the electricity cost and the public incentive to buy solar panels are high.
If you can sell the electricity at retail price (sometimes maybe higher), it doesn't mean you are paying the same rate because your costs may have been higher.