Anything's possible... likely? No, it will take you millions of years to find a block on average. As for why they sell them to you, it's because it's easy to sell hardware to people who don't know what it is they're buying if the sales pitch is all bullshit.
I bought on Amazon UK, And sales pitch was that I could earn at least 25 bitcoin per month. If that's really not true I will raise an issue with Amazon
Probability of earning 25 bitcoin every month pretty much ZERO.
You MIGHT get lucky and get a block once a few DECADES.
I'm currently running a little over 7 TERRAHASH and pulling in on average a bit more than 1 bitcoin a MONTH (pool mining via Slush's pool) - which has been dropping quite a bit due to high diffuculty increases since the release of the S7 and especially the release of the Avalon 6 (and ramped up production/sales of both).
IIRC the Block Eruptors had a highest version around 350 MH - that's less than 1/20000 (yes, One over Twenty THOUSAND) of the hashrate of my current Bitcoin mining setup. You do the math.
