Anyone Know If Sleep Essence, The G2z Series, Mattresses Are Good? And How Much Are They?

I just wanted to know if anyone knows about Sleep Essence mattresses, the G2Z series, because someone is trying to sell me a queen pillowtop made by S&E its called Retreat, the G2Z series.. for 500.00 and I wanted to know if that is a good deal or a scam!! Please help, I researched the web for it and can’t seem to find anything!! Thank you!