Diamonds report

Recently I have been looking into information on diamonds.

Namely the 4Cs or 5Cs we will talk about will be discussed briefly as follows:
Carat,
The size and weight of a diamond, bigger it is the larger it is.
Colour,
D to F refers to the white/clear zone, G and below will be termed as discoloured type and usually refered to as lower grade diamonds.
Clarity,
Flawless, Internally flawless, very very small, very small inclusions are the typical choices, frankly, very small inclusion range is good enough as you will not see the inclusion unless with a 10x loop magnifying glass.
Cut,
Cut grade depends on other aspects such as polish and symmetry of the diamond, besides the shape of the diamond, cut grades also determines to shine of the diamond. I will emphasize this for shining diamonds.
(Cost)
Cost of diamond , another important factor. Buy within your budget and get good quality as far as possible.

There is a lot more in determining what is an overpriced diamond.

There is a rap-chart which determines the per-carat-value of a range of size diamond.
With very little inclusion and fine cut grades the value of diamond can go up to twice their rap-price (tip-top).

Undermining this, one needs to know how much "overprice" are you paying for some of the reknown cosmetic cuts or fancy cuts.

A gauge is Tiffany rings often is twice or thrice the amount that you could get from the market value of a norm ring. Destinee is about twice of market value. Brilliant rose is a bit more than twice.

So for value-for-money chooser, one will steer off these cosmetic design.

One important factor to take note, is that a diamond does not really "shines" greater with more facet, cuts. It also depends on the symmetry and proportion, polish etc.
More facet could means more small sparkle instead of a bright sparks too.

This depends on individual preference for something different.