How much, of course, depends on the recipe. And, not to complicate your world unnecessarily, but you'll need *more than one* type of malted barley and/or some brewing-specific toasted/kilned or roasted barley, if a recipe calls for it.
But, yes, an average total grain bill for a five-gallon batch is 10-15 lbs., for many types of beer. Some recipes call for a little less; some call for a bit more. (Did anyone see that "Blackwine" recipe in the last Zymurgy
? It had something like a thirty-pound grain bill!)
I'd strongly suggest reading more about all-grain brewing, after you've read about the different types of barley (and wheat and rye) used in brewing, as posted above.
For starters, try http://www.howtobrew.com/section3/index.html
In the States, a good price for a simple base malt, e.g. domestic 2-row, US$1.30-1.50 per pound, ground. You could find some for a little less, and certainly for more. You will need to grind your malt or try to get the brewery to grind it for you. This is not an option. If you can't get it ground, you could roll a heavy glass bottle (wine bottle) over the grain in a pinch, but don't pulverize it.
But, don't get discouraged. Throughout history, the best brewing comes from invention and creativity. Keep posting here to tell us how it comes out for you.
When I lived in Korea for a year and a half, I missed good beer. "Oriental Brewery (OB)" and "Crown Super Dry Ice Light" wasn't doing it for me, nor was "Bu-du-wa-i-sa" (Korean-brewed rice beer with Budweiser labels, in Hangul). But then I discovered soju and forgot what beer was.
Best of luck to you!