Not all blades are created equal. The blades in the OP are obviously cheap ones that were used well beyond their lifespan.
I have a set of Oregon gators on a few different machines going on a few years now. They are heavy duty and hold up extremely well and can be sharpened multiple times.
My grandfather mows 7 acres weekly with his Scag 3-wheel mower. His field has some rough areas, and he was replacing cheap blades constantly. Even the cheap blades were $18 a pop. I put some Gators on there and have been sharpening them once a year for the last 3 years or so. The blades were more expensive initially, but provide a better cut and have lasted much longer, saving money in the long run.