Vanilla Extract....What is the Difference between them?

Does Anybody Know about Vanilla Extract Differences?

I just bought a bunch of vanilla because it was on sale..McCormick pure vanilla extract for$2/per 1 0z. bottle. But then I saw Adam's Extract, pure vanilla, not imitation, for $6.50 for a 4 oz. bottle.

I bought one bottle of Adams and four bottles of McCormick (my usual brand.

But then I saw Spice Island's bourbon vanilla, which was $30 for a 4 oz. bottle.

Okay, so what's the difference? I can't figure it out! Even in catalogs, they list Mexican vanilla, which some have said is good, others have said vanilla from Madagascar is best.

What do you think? I plan on trying the Adams just to see if I can tell any difference. I wonder why it's so cheap? It has the same percentage of alcohol as the McCormick. Hmmmm.....I'm confused!