Cheap engagement ring

My boyfriend, and I would love to get engaged. I know a ring I would most likely fall in love with is out his budget if bought at a retailer such as Kay's.

I happen to look at ebay.

There is a thing I happen to like

1ct. (fake)

D-vvs1 gold 14k

And it's badly 200.

Why is it so cheap? My friend got his ex a sliver ring with a fake diamond, and he spent $500. My ex got me earings that happen to be sliver, and fake diamonds as well, and he spent a hundred.

So why is this ring so cheap? I don't want my him to buy something and get rip off.

How do I know if something is a steal or a simple rip off?