A: How to convert milligrams to money: 

“Top-quality” CBD products with less than 1,000mg of CBD “should cost” about $5/100mg. 
Products containing over 1,000mg “should cost” about $4/100mg.

500mg is a $25 value (6 x $5 = $25).
1,500mg is a $60 value (14 x $4 = $60).

This calculation is a rule-of-thumb based on the current market. Consider current and future market standards of quality, drivers of cost, and constraints on the industry. 
Other evaluations are welcome— what are your thoughts? 
These prices reflect the current value of “top-quality” CBD extract, not the value of the other ingredients in the product. 
If this hypothetical 500mg or 1,500mg product were a CBD-infused 2oz container of lotion or a 1oz tincture bottle, one must account for the value of the infusion process with said lotion or carrier oil and any other inputs, like terpenes. 
Top-quality terpenes add expense but a small amount goes a long way. So expect to pay a little more for products with well-calculated terpene profiles.
Finally, consider the costs and time involved in bringing a product to market. 
You can’t rush perfection but you shouldn’t over-charge for it either.