And why can't you sell the seeds? The article quotes ~$100/1k seeds. That's $0.10 per seed. There are ~250 seeds per pumpkin - that's $25 per pumpkin. What am I missing?
For an F1 hybrid you need to do all this work to maintain each of the pure lines, and then also do the cross. Once you have the fruit, the seed needs to be separated, dried, perhaps tested for viral, bacterial, or fungal disease, perhaps treated with fungicide, and tested for germination.
Of course a random pumpkin seed will grow with some probability, and the resulting plant will bear some kind of pumpkin. But the cost of high-quality seed is a very small share of the total cost of growing a pumpkin, so it's not a good place to cut corners.
ETA: And the article notes explicitly that those seeds were hybrids. For emphasis, saving seeds from hybrids may or may not be legally permissible, depending on the patent status and any contracts signed, but with very few exceptions it doesn't work--the genetics aren't stable, and the F2 doesn't reliably have the same desirable traits as the F1.