You missed nothing. Hashflare missed to add all costs to info site, so that customers get trapped. There are not only maintance fees, but also electricity costs, that vary from pool to pool, whyever. In the last months, before Hashflare anounced, shortening lifetime contracts, there was even a ROI of 6 months. But most of the time it was on 22 months. Now they have a ridiculous withdraw minimum, that most of customers will never reach.
So, forget hashflare. I would categorize it as scam.