A lot of that depends on what scale you’re using. If you are comparing apples to apples raw coffee is normally about half the price of roasted. Coffee pricing is a lot like wine pricing. Rarity or quality both have their influences on price.
Even comparing green coffee against itself, a pound of green microlot Colombian is going to be more expensive than a pound green from a larger commercial farm. So you’d have to compare the rarity of the coffee against each other. Not all wines are the same just as not all coffees are the same.
There’s no comparison AT ALL between fresh roasted coffee and a can of coffee. That’s a quality issue.
If you are comparing whole beans coffee in a grocery store against home roasted coffee the margins may be a little closer, but you are adding in the element of staleness in the store bought coffee. …How long did it take for that coffee to be roasted, packed, get on a truck, get to the front of the shelf, and finally get used up at home?
And, don’t be fooled by the 12 oz pound pricing! a real pound is 16 ounces, so factor that in.
Once you’ve accounted for quality, scarcity, freshness, it’s very close to half the price roasting coffee at home. Its hard to beat the consistency of what a professional roaster can produce from her specialty coffee shop, but, its going to cost you half as much as doing it at home. Its a lot like going out to dinner.
Your friends will also be completely knocked out at how good your coffee is. THEIR coffee will taste like swill 
while costing twice what yours did. That’s well worth the ten or so minutes at home to roast up a batch or two, just in bragging rights.
Raw coffee beans store well, a year or so. If you buy raw coffee bulk it will always be as fresh as possible once roasted, and always roasted exactly the way you like it best. Store bought coffee has about the same shelf life as bread, or milk. So there’s a big tertiary saving in roasting your own right there.
Currently the market is crazy. Coffee prices are through the roof. The mega-corporations have held back their price increases as much as possible over the last year or so, but they’re also sitting on coffee they bought 3-4-5 years ago. Sooner or later they are going to have to buy current crops and as we’ve seen recently, even the corporate giants will raise their prices and the margins will once again be closer to half the price.
Overall, Its the difference between corporate food and fresh homemade food. Homemade is better, less expensive, and just takes a little love to produce something spectacular. Its worth the effort.