Use in Natural Medicine
First, I thought I'd thumb through my book, The Herbal Drugstore, to see if they recommend the use of essential oils. Sure enough, I found recommendations for tea tree, lavender, geranium, peppermint, bergamot, and clove essential oils. The book recommended using these oils externally or topically, for things like respiratory and skin problems.
Network Marketing vs. Retail
Then, I hit up Mountain Rose Herbs and Young Living to find a ballpark cost to these recommended oils. These days most people get their essential oils from Young Living and DoTerra, which have become popular network marketing companies. However, unless you are a distributor, network marketing is almost never a good deal. Case in point:
Clove Oil (1/2 oz.): YL - $20.07 ~ MRH - $7.50
Bergamot Oil (1/2 oz.): YL - Out of Stock ~ MRH - $16.50
Peppermint Oil (1/2 oz.): YL- $28.29 ~ MRH - $7.50
Tea Tree Oil (1/2 oz.): YL - $34.21 ~ MRH - $6.25
Lavender Oil (1/2 oz.): YL- $30.92 ~ MRH - $7.69
Geranium Oil (1/2 oz.): YL - $54.28 ~ MRH - $18.75
So first of all, don't buy your oils from Young Living. If I wanted to get the same price on Young Living geranuim oil as MRH, I would have to sign up as a member (up to 40% off retail) and sell $172 worth of product. That sounds like a lot of work! Of course if you really want to work your way up through the company and have a bunch of people under you, you might be able to get some pretty cheap oils. But unless you have a ton of potential customers (popular blog writer, speaker, etc.), you'll end up paying more for Young Living oils, even as a member and distributor.
Now we tackle the next problem. My herb book recommended the use of six essential oils. Young Living (and therefore, most people who tell you about essential oils) recommends the use of all 84 of them. They recommend stirring a drop of peppermint oil into your herbal tea to aid digestion. But what about just drinking peppermint herbal tea? If you grow your own peppermint, it's certainly cheaper than using essential oils.
I was surprised to see oils like black pepper, carrot seed, sage, chamomile, goldenrod, dill, and coriander. They've come up with an oil for everything! Mountain Rose Herbs was selling a 1/2 oz. bottle of catnip essential oil (of all things!) for $40. Crazy! Some of the most expensive oils are made from the cheapest plants in your backyard. A homemade tincture would cost pennies on the dollar.
The Bottom Line
If you want to get into herbal/plant-based medicine, essential oils are a very easy (but very, very pricey) way to do it. No one who is trying to save money should get into essential oils. I would recommend buying only a few, or sticking with the cheaper oils (lemongrass, orange) to scent homemade soaps and cleaning products with. These are the oils I have: peppermint, spearmint, eucalyptus, lavender, lemongrass, citronella, and patchouli. Two are from a local mint farm, and the others I got from grocery or craft stores. I've had most of them for several years, so as you can see I'm not a heavy essential oil user.
As you can imagine, building a "medicine cabinet" primarily with essential oils will easily cost hundreds of dollars, especially if you buy through the more popular companies. I believe that the medicinal value of most essential oils is sketchy, and the price is not worth the benefit that oils might provide. I only use essential oils for respiratory problems (homemade vapo-rub, etc.), and even then, there are cheaper ways to sooth a sore throat.
If you are interested in natural medicine, I would instead recommend buying and/or learning how to use herbs. Herbs provide most of the same medicinal benefits, but will fit any price range.
Do you use essential oils? Why or why not?
*Edit 9/14/15: I would recommend using LorAnn oils for regular external use and for things like cleaning, soap-making, etc. These oils are therapeutic grade, 100% pure and very affordable, ranging from $3-$10 at Walmart. Walmart carries almost all of the common oils like eucalyptus, clove, orange, etc. Other oils are also available on LorAnn's website. The most expensive oil on their site- myrrh- costs about $30 per ounce.