My local homebrew shop sells one ounce of hops for $3-4 dollars a piece. I can order a pound of hops for around $21-24. If I bought that much locally I'd pay $48-64. Huge discount buying online. (I've been happy with orders from http://www.hopsdirect.com but there are others who sell for equally cheap prices -- some allow you to buy cheaply by the ounce.)
The benefit is that if you buy some general use hops in bulk, you can run through them reasonably quickly and reduce having to keep multiple varieties on hand. I have a pound of Fuggles I've successfully used in a red ale, brown ale, blonde ale, and porter, and I'll use them in several Belgian beers and I'll likely use them in a stout and several other beers. It's amazingly cheap.
The problem if you buy in bulk, you are stuck with a lot of hops and since the alpha acids decline over time, you have to properly store them or use more and more to get the right alpha acid content for your beer. I freeze mine in freezer bags, but to truly retard breakdown, you need to use oxygen barrier bags like what you buy hops in. (This problem can be eliminated if you split an order with other brewers or buy from somewhere that allows you to buy by the ounce so you don't have to keep much on hand.)
For a homebrewer that enjoys hoppy beers, I can hardly imagine how you can afford to brew and not buy in bulk. Hops are an expensive part of homebrewing.
If you are fond of making recipes, and I do, you can very efficiently burn through a pound of one (or two) kinds of hops by adjusting or building recipes to favor the hops you buy. That's why I have developed so many recipes using Fuggles. Fuggles are fine; I just happen to have a lot so that's what I use. Again, I don't like hoppy beers, so it's not a big deal to use some Fuggles for bittering and a little for flavor and aroma.
You can do this with an American breed for IPAs (e.g. Cascade), any of the English breeds for English beers, a German breed for wheat beers and lagers, etc. You would be surprised by how good the use of a single hop can be in a beer, especially if you're making a simple session beer.