Mustard: I will spend ridiculous amounts of money for fancy mustards. I love mustard and use it on all sorts of stuff besides sandwiches (salad dressing, chicken roll-ups, eggs, etc.).
Raspberry-Chipotle Sauce: Fontana Farms is one source for it, they also sell it (although a different brand) at Cost Plus. It's great on chicken and in sandwiches. I also make little pseudo pizzas with pitas and use 1 tbsp as a topping instead of tomato sauce. It's very spicy so a little goes a long way.
Fresh Fish: I get it from my local farmers market. Sometimes it has literally been caught that morning and is so fresh you can eat it raw. It costs a small fortune but the taste is so superior to grocery store fish that I can't eat the store-bought stuff anymore.
Pickles: I love pickles for a snack and will spend any amount of money for something new and different. I spend $10 to get a quart jar of dill pickles from a stand at my farmer's market, but they are the best dills I've ever had (and no sugar added). The same stand also makes a really low calorie veggie soup that I also pay $10 a quart for.
Also, balsamic vinegar and other high-end vinegars. I try not to think about how much they cost.
And I'm not sure if these count but also:
- Light chevre from Trader Joe's. I love this stuff and use it in any recipe that calls for cheese. I also eat it on sandwiches.
- SnacLite PowerPB. 80 cal per tbsp, half the fat, twice the fiber, and twice the protein of regular peanut butter. And it tastes like peanut butter and has the same consistency as peanut butter.
- Penny's Low Fat Muffins