I think it's safe to say I go through a LOT of vanilla extract with all the baking I do. About a year ago I decided to look into making my own extract. After perusing a few sites, I found that it was actually ridiculously easy to do, and could be mildly cost effective, too; just takes time.
Someone actually went through the bother of calculating the cost difference, but basically I was spending $5 for each bottle of Bourbon Extract at Trader Joe's which only took me 1-2 months to polish off. Making it yourself doesn't save you a ton of money in the long run, but at least I have 1 liter batches to work with at any given time.* And you can say you make your own extract. I think it's worth the 6 months wait time just to say that.
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The other beauty of this plan is that you can make however much you want. A recipe from Simply Recipes gives you a 1 cup option. As much as it is technically science, I don't think you could really screw it up however you decided to mix it up. Just don't add simple syrup. You just don't need it, and I think it detracts from the extract if you do add it.
* If you're curious about my calculations, I spend approximately $20 on a bottle of vodka, plus about $10 on the vanilla beans (including the cost of shipping). So, $30 that is then split into approximately (8) 4 oz. batches makes them about $3.75.)
Also, I bought the beans at beanilla.com