When we were in Bali (just a little over a year ago!), I made it my goal to buy vanilla beans in bulk. I bought a lot. I don't remember the exact amount, but maybe 5 pounds or so? Either way extract is super easy to make! I'll share a basic ratio that I got off the internets and you all can do the math to make as much as you want! The vanilla bean insides (caviar) settle to the bottom, so if you wanr them to show up in a recipe (ice cream perhaps) just shake up the jar!
1 cup vodka
3 vanilla beans
That's it!! Slice the vanilla beans in half, leaving one inch intact. Place in mason jar, and pour vodka over beans. Store in cool, dark place. Give the jars a good shake every so often. Ideally you want to wait 3 months + for the most flavor, but I've seen sites say 1 month is ok.
You can also use bourbon instead of vodka. I personally prefer vodka.