Paying 1 BTC now to get 0.5-.6 BTC later is a losing move. It doesn't matter what bitcoin does, it can go up, it can go down, it can stay exactly the same as it is, you willingly, of your own free will, gave them money now, to get less than that back at some point in the future. It doesn't have to be a Ponzi scheme, you lost money on this deal either way.
I don't happen to agree with you. The Bitcoin I spent on this mining contract costs me approx. $435. If, for the sake of argument, the price of Bitcoin goes up to $600 or $700 or higher, the value of the Bitcoin I am mining goes up as well and it becomes a much more attractive value. That is simple arithmetic. Maybe PB Mining is counting on this as well. According to everything I read, the general ongoing acceptance of Bitcoin worldwide and Wall Street's new involvment, I would say that's a given. Only time will tell. So far I have not lost a dime. I am certainly making more on my investment than a savings account, money market fund or the stock market. If, and it is a big if, I get ripped off, I will deduct it from my taxes and move on. I don't feel like playing the safe game. It gets you even less.