Just to benefit other bros who are looking for their first proposal ring and are confused about the diamond pricing, below is what Sam from JP just emailed me. Patient and nice guy. Can see why they are so popular around here.
"Diamond prices do increase significantly when it passes certain carat weights, such as 0.30ct, 0.40ct, 0.50ct, 0.70ct, etc
Hence, this is why we do not carry these flat carat sizes. Anything with a 0.3xct, would be fine.
In addition, when we purchase our diamond from cutters, it comes with discounts. Carat sizes nearer the the flat carat sizes, usually gets better discounts.
Eg. A diamond cutter would give a discount of -15% discount for a 0.51ct and a -8% discount for a 0.58ct.
By providing more discounts for the lower carat size groups, it lessens the price difference in the price jump.
However, that being said, a high 0.4ct+ Eg. 0.46-0.49ct, is hard to come by, as diamond cutters do prefer to hit the 0.50ct+ mark to sell their diamond at a higher pricing, even though if it means reducing the quality of the Cut.
In terms of relative proportion as well, say a 0.97 G VS2 will approximately be under $12,000, a 1.01 G VS2 will be $14,300."