those sales guys do work on commission.
the more expensive products..you're paying for marketing hype. cell-tech is a great example of that. they take plain cheap creatine, mix in powdered kool-aid, and charge you about $1.50 per serving.
you can get 100 servings of creatine for $15. I think that's 15 cents a serving. Dextrose is $5 for 100 servings.
So, 20 cents if you make it yourself, or a 750% mark up to have MuscleTech do it for you.
super dirt cheap stuff probably isn't the highest quality either. but you don't have to go much higher to hit the good middle of the road, quality stuff that isn't trying to trick you.