Quote from Option Trader:
I think I now have the answer to my question:
In as much as there are bears who would pay huge carry costs to short the stock, some would rather buy the puts; however, that is VERY expensive, hence they sell the calls as well of the same strike price, (and even offer a synthetic long stock position to others at a reduced cost). The net result is they benefit from the downside for a cheaper price than shorting the stock. Hence, they are currently offering e.g. to buy the June 1 calls at $.20 (or $.25), and bidding to buy them at $.60 (or $.55), meaning they are offering their counterparty to get the upside for $.60 to $.70 instead of the current market price of $.737.