Diamonds

Well first of all, there is no difference between a lab grown diamond and a natural one except for the way it was created/formed. The only way someone would be able to tell it's lab grown is by using a magnifier to search for a laser inscription on the girdle (the edge of the widest part) of the diamond.

Diamonds are definitely a luxury good as they don't maintain their value and can usually only be bought overpriced. So unless you're rich or believe that price is equivalent to affection you should check out some alternatives such as moissanite. Moissanite is the second hardest natural mineral and is pretty much just as beautiful as a diamond. It is also very very similar appearance wise to a diamond. So similar that most people would mistaken it for a diamond.

For 700$ you could buy a moissanite ring whose diamond equivalent would cost around 10 grand.