Coinwarz dont include increasing difficulty level in its calculation as it is unpredictable. Bitcoin difficulty increased 39%(average) per month. Though it is expected to go higher year by year lets assume it is the same this year.
If Btc stays the same for the next 12 months

• In 4 - 5 months the diffculty level will reach a point that daily mining rewards will be less maintenance fee
• Hashflare stops mining if the mining is in loss for 21 days.
• Every month after that will be more difficult. Hence no mining for the rest of the contract.

So most likely you are going to end up with less than $350.

It is a huge loss investing in hashflare when yoi consider prices are staying the same.