Sure, that 2002 St. Jean Chardonnay got a 98 from Wine Enthusiast … but is it really worth what they’re charging? And how much should you pay before you’re paying too much?

You might be interested in a subscription to QPR Wines, a wine-buying guide that (among other things) does the math for you. The QPR formula takes the average retail price of a wine with a given score and divides it by the average retail price for all wines with that score. The result is a percentage – and the lower the percentage, the higher the value.

Let’s say, for example, that X Pinot Noir (with a score of 89) costs $20 at your local wine store. QPR has compared all Pinot Noirs with an average score of 89 and found that the average price is $42 a bottle. So – at less than 50 percent of the average retail price – your $20 bottle is a great value.

Of course, Michael Masterson warns, when a wine gets a high rating from Wine Spectator or Wine Enthusiast – and is priced well – your chances of actually getting your hands on a bottle are extremely remote. But if you are willing to be a little flexible, this service can help you get the best wine for your budget.

QPR’s wine-buying guide is available via e-mail, 18 times a year, for about $35.