This is mainly because the ordinary vegetables are actually mutated.
Let me explain a bit further. Over the hundreds of thousands of years since farming began on this planet, vegetables have evolved immensely. Humans have used herbs as well as certain medicines, spices, and other things to change the way vegetables taste--and look. As the years progressed, the vegetables changed in size too (the corn that we eat at barbecues and parties, the ears of corn, are actually very far away from the size that corn used to be. If you look at the small corn used in Chinese food, that's extremely close to the original size and taste). That being said, the ordinary vegetables you see in markets and grocery stores are mutated to taste and look the way they do today.
Organically-grown veggies, on the other hand, are closer than the store vegetables to their ancestors. They need special care, property, and time to grow in a different way than the mainstream vegetables (they're like hipsters, if you will). Organic veggies are healthier, but also more expensive for their special needs. That's really why they are sold at special stores and why they are so much more expensive than one would think.
I hope this helped!
History Courses as well as Modern Foods classes