K&G is a great shop (I'm biased, because I'm a fairly regular customer there) but you're right - buying your base malt by the pound there is ineffective. However, their bulk prices are very reasonable. The only place I've seen cheaper on sack purchases is the DC Group Buy, which is kind of a pain in the ass if you live out this far. I buy 50lb sacks of 2-row and Pilsner from K&G, and grab the specialty grains I need as-needed from their per-pound bins. Keeps my price/batch fairly low.
The per-ounce hop bins can also save you some money over the packaged hops as long as you're buying them the day you're going to use them. I'm not sure what the prices are on the pound bags of hops there.
They also usually have a pretty good selection of commercial craft beers there.
BrewLoco (also a great shop) has better prices on the per-pound grains, but not as much of a selection on grains/hops/yeast/equipment (and a comparable selection of commercial craft beers)
Loudoun County is surprisingly a great place to be a homebrewer now that all these shops are popping up, with some unique experiences for brewing. For example, both shops mentioned above sell JasperYeast, which is a yeast company started by one of the brewers from Lost Rhino, with some of the strains actually harvested in the wild by him from around the area. That's pretty cool in my mind.