Mushrooms (Never pay more than $5.00/lb for Shiitake mushrooms!)
Szechuan pepper-corns? You gotta go ethnic. Seaweed? No-brainer: skip Nature's or Wild Oats or Whole whatever. If you're in the NW, Uwajimaya will work just fine, even though that's pretty upscale itself. They do have simply the best fruits and vegatables, bar none, and you pay for 'em.