Amazon's dead-set on killing off the grocery store, with a same-day delivery service and even a Dash gadget for restocking items around the house. Now the retailer's going one step further, taking on Costco and Walmart with a new program called Prime Pantry. If you're a Prime member living in the 48 contiguous states, you can ship 45 pounds' worth of household essentials -- in "everyday sizes," not in bulk -- for a flat fee of $6. (Yes, that's on top of your Prime membership payment.) Amazon told us the items available include "popular soft drinks and bottled water, a new range of paper and laundry products in popular pack sizes, single boxes of breakfast cereal, potato chips, convenience-sized personal care products and more." Rumors about an Amazon Pantry service began circling late last year, and while the service is live now, the company hasn't formally announced it.