I have found 9x out of 10 you get exactly what you pay for. A local company has these made with their name on it from a small manufacturer. They are not cheap, but a little less expensive than the big name brands and last just as long if not longer. http://www.jiscodirect.com/index.html
I buy their jumbo flap discs in 40 mostly, 80 if I'm polishing up SS.
I will also only buy Carborundum Gold 6" cut off wheels, don't chatter or wander when you start, cut fast, don't chunk, and last all day, and they don't come apart no matter what you do to them. I've seen too many people get hurt from cheap cut off wheels.