"We trust that Bitcoin mining will be profitable in May as well or all the Bitcoin mining will stop. The online profitability calculators are wrong just because nobody in the right mind will keep doubling the hashrate of the network every month if they are loosing money. The hashrate of the network will keep growing only if the bitcoin value goes up again. For this reason and because we provide the lowest prices possible we do not think that our miners will have a negative return of investment. However, we understand that you might not agree with us and we'll offer you the refund if you decide to go ahead with it."
Difficulty jumped by about a billion Saturday.
First a little bit of chartism for the serious investors

lol
If you make a quick analysis of the Bitcoin chart the price has a strong support in the zone between 370 and 400 $ (the lost of this support means the price will drop deep to the bottom) in the other hand the next resistance is first the 560 $ (200 days moving average) and after that the zone of 600 $ if the price can break this resistance in the next days/weeks we will see the beginning of a bullish trend. In my opinion this option is more probable but of course I can be wrong.
Second."nobody in the right mind will keep doubling the hashrate of the network every month if they are loosing money. The hashrate of the network will keep growing only if the bitcoin value goes up again." I think this is only half true because when the price go down a lot of orders remains undelivered (same if the price go up) so the network difficulty don't follow the BTC price in real time but with a lot of delay.