You're not taking into account the possibility that:

- Ether could crash
- Ether mining difficulty could spike over time and result in your returns per day going down
- Your contract terminated because of the combination of these two factors which results in your maintenance fee being unable to paid back.

The thing is, your cloud mining contract will always start off well and over time, as difficulty increases and mining rewards essentially lessen, you're going to be making out most likely a loss at the end of the day.