The all-mustard vendor in the Market is Kozlik's as noted above.
Last time I was there, it was $6 per jar...........its not only really good mustard (some of the best in the world); but they also have 30+ varieties.
You can get Green Peppercorn Mustard, an Orange and Ginger mustard, a Sweet and Smokey, a Curried Mustard and even one based on Black Harp.
Worth every penny!
Pre-pandemic you could also taste them all, as they had pretzel's out and sample jars.
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There's so many other great products there and most are priced reasonably. Certainly there are some gourmet items (venison tenderloin, obscure blue cheeses, wild mushrooms etc.) for which you will pay a material sum
But there's also lots of opportunity to buy stuff at great prices.