The Vault is indeed an opportunity to win a bottle worth much more than the $20 price of admission, and again, you'll always get a bottle worth at least what you paid.
Please note that the $20 value is based on public retail prices, but we understand that if the wine is out there for less, it might not feel like a win. If you haven't had a chance to check out the probabilities for the Vault, you can see those here (as well as a real-time preview of wine in each reward tier).
The whole system is completely automated and resets every 1000 bottles. We balanced the Vault to offer the highest percentages of high reward tiers and basically break even. Good Luck!