I'm not familiar with metals by name but the it is brittle in the cheapies, no strength to it whereas in the high end it's spring steel. Any tack used in an english saddle is blued so it doesn't rust or react with the chemicals involved in tanning leather. In the cheapies the staples rust which deteriorates both the staple and the leather which results in the staples either falling apart or falling out. What scares me is people use these for jumping. In 2001 I received and email and pics of a gal who'd bo't a pretty saddle off ebay
for around $125. Of course the pretties had appealed. On her first trail ride the horn broke away from the tree and was hanging on by a flap of leather. Before she got home the tree snapped and she had to walk. Could I fix her saddle? No. I have a pic somewhere of another a gal had stripped down and sent pics. Cracks in the hollow fiberglass tree. The cinching was their version of a sam stagge rigging badly done. Cinch pressure had caused it to break. That saddle lasted only a couple of leisurely rides.