Yep, whey is whey, but you're paying for the other stuff... or lack of. Alot of what you're paying for is the filtering process. The more expensive brands that use only the isolate runs everything through filters. This takes the "junk" out, so saturated fat and cholesterol is pretty much gone. The amount of protein per serving goes up since the extra crap is gone, and it's much easier to mix. The good stuff can be stirred with a spoon, while the cheap stuff has to be shaken aggressively in a water bottle or martini shaker since it clumps up so bad. Also some products such as American Whey will add sweeteners like fructose, which makes it taste better, but some people are allergic to these additives. American Whey is both filtered and sweetened so it's pretty expensive compared to alot of products.