That is a big price difference! I don't know anything about them myself. I finally ended up with Ferrodo DS 2500s for my big brake system at $128.21 plus tax per axle. I have been VERY pleased with them. No dusting, no squeaking, and they seem to grab better when they get heated up! My Pagids were extremely dusty and major squeaking on the street. Everyone I have sent the Ferrodo way has been extremely happy with them.
I have EBC yellow pads on my car, they work well on street and track. When I bought them the cheapest that I found them was about $100 per axle. $50 would be way below wholesale meaning either the seller is taking a big loss or going out of business. I guess they could be Chinese copies but that seems unlikely. That would be a great deal for pads you will love on the street and like on the track once up to temperature. They feel dead when warming up. Also low dust if you are lazy like me.