The organic section at my store isn't even a full shelf, but they have other vegetables that are perfect. They have collard greens, mustard greens, spaghetti squash and butternut squash! But would they be safe to feed my dragon, or world I have to clean them with something? I really hope I can, can anyone speak from experience feeding a dragon stuff just from the normal shelves of their supermarket?
Sure I feed veges from the regular section at the market all the time. I just give everything a good rinse when I get home just as I would with food that I eat. I found that cutting greens up after rinsing them and putting them in big ziploc bags with some paper towel keeps them fresh in the fridge for quite a long time as well.
In the US "certified organic" is a regulatory term; it requires adherence to a set of standards (notably limitations of allowable chemicals such as glyphosate and sewage sludge) as well as certification. The extra price is a result of the certification cost as well as the differences in farming methods.
I've not seen info on nutritional content variation (this would also be effected by region and climate etc and is an interesting topic I may look into more) but if folks have opposition or concern over conventional farming practices it's an option.
Personally I use both conventional food and organic, whatever is the healthiest and at a reasonable price at the store.