Now is a good idea to buy some s5/s7 ghs. a virtual antminer s5 costs 0.63BTC 
where do you see that price? when i go on hashnest the virutal price for a s5 is 1.12905359BTC
Indeed but prices continues continue to slip, I would wait until next difficulty adjustment as it will likely be another big one.
Megatron you get the s5 at that price by buying hash on market.
This is the biggest issue. As they add S7 the prices just continue to slip which you will just about never ROI until the difficulty levels out for some period. Only issue with that is the price per gh/s may still slip if btc price rises in the near term with the expectation of the halving.Megatron you get the s5 at that price by buying hash on market.
It's almost to the point where playing with Hashnest is a losing game for everyone except Bitmain.