Your potential for savings is based completely on which wines you choose. If you always choose the most expensive bottles (above $40 for one credit and above $80 for two credits), you'll save a bit. You can also end up paying more for the plan than you would just buying the wine, especially if you are eligible for a TIW card discount that you will be using over a year.
In some cases the only advantage the wine plan will have is the convenience of having even your alcoholic beverages prepaid, which sometimes means more to people than saving money.
I also don't think the fact that a wine costs more necessarily means I would like it better, but if you're out to explore wines based on their price point, it might be worth it to get the plan.