The higher quality, naturally, gets a better price also. So, if you are getting a good harvest of quality products, you will make even more money. I hate to garden, so I do a "cheat" and have a garden that I saved that has perfect plants. I take what I want for my sim family to use in cooking, eating and alchemy making and sell the leftover to the consignment shop.
Fruits/veggies are used in making elixirs also, so they sell good at the consignment store, I think you can sell anything there; books paintings, gems, gem dust, artifacts, I think you can sell it all there. I need to check that out, selling artifacts, books, paintings, and other items.
There are several different types of gardens in the swap shop that can be downloaded into a game. Place them on a community lot and you don't have to do the weeding, watering and no dead plants to deal with.