A large bottle containing a lot of oil does not mean there is a lot of CBD inside. You should only be interested in one thing, which is how much CBD is in a product.
For example let’s compare a 10ml bottle and a 30ml bottle, both have 2000mg of CBD. The 30ml bottle will require three times as many drops as the 10ml bottle for the same amount of CBD. Don’t buy based on volume, buy based on CBD strength in the product.
We often feel like we’re getting more for our money with a larger bottle, but all you’re getting is extra carrier oil which you might as well buy at the supermarket.