Its a scam similar to the get $500 gift card or what not for completing these offers. The things you have to do to get the stuff is overpriced and the overpaying more than pays for the items you end up getting.
At one time there were a few similar offers that could be exploited e.g. you wouldn't have to pay too much to get the item, but those mostly disappeared.
Also thats assuming that you actually get the items promised for completing the offers. Theres a decent chance it will be a complete scam and you get nothing.
To summarize i wouldn't touch this site or any like it with a 10 foot pole.