Notice differences in cost. Infused oils tend to be a lot cheaper than essential oils because they don't require the same extraction processes. (They don't require a hard-to-extract oil to make up the bulk of the product.) If the oil you are buying seems very cheap, it is probably infused rather than essential oil. Essential oils will typically cost $8-15 for 0.5 ounces (15 ml). Infused oils will typically cost $4-15 per ounce (30 ml).