CBD is similar to consumable vape products as they are offered in Milligram strengths and are priced out by MG per serving, not ML of Liquid contained in a bottle .
The amount of CBD per serving is based on how much you ingest. For instance, 1000mg of CBD in a 30ml bottle will deliver 33.3mg of CBD per serving. A server being one full dropper which is 1ML.
1000 MG / 30ML bottle would be 33.3 MG per serving (1000MG / 30ML)
500 MG / 30ML bottle would be 16.66 MG per serving (500MG / 30ML)
1000 MG / 10ML bottle would be 100 MG per serving (1000MG /10ML)
Pricing of CBD is not based on ML, it is based on MG of CBD. In the above examples you would most likely pay the same for 30 ML and 10 ML bottle containing 1000 MG of CBD and less for the 30 ML with 500 MG. Industry pricing is based on MG of CBD and not the size of the bottle.
Pricing on other products like edibles and creams work in the same manner. Always about the MG of CBD.