Mystery boxes

I have been seeing more and more quote mystery box and envelope raffles. What is up with this? Are these scam artists or legit? It seems like a huge rip off. Some of these lots promise ps3 xbox etc. Some sell for like 500 bucks. Sounds risky whats up?

Its a gamble alright.
The envelope raffle is easiest to explain, they sell so many envelopes (say 100 @ $10 = $1,000)and give each buyer a number, an alledged envelope for all buyers - they are opened and the ones with money in are then credited to the buyers Paypal account. The total number or value paid out will be less than $500 otherwise its not worth doing.