Paying for Dirt?

First off, let me say the idea of paying for dirt baffles me. I  moved here from Southern Oregon and  we planted everything right into the ground in our nutrient rich soil! Here in Florida, the soil is basically just dirty sand. So we went to a local nursery and got a yard of good top soil for garden bed #1. It wasn't enough to fill the whole bed, but it was close. Justin made the garden box 10x4x12. We are about 1 week in and  I have 2 tomato plants, and 3 pepper plants planted, plus 2 rows of purple dragon carrots planted, and my starter seeds we planted last week are now sprouting. Things are going pretty good so far. We also picked up some more wood this weekend to build 2 more long skinny garden beds.  I plan to use them for Green beans, Broccoli and Cauliflower. Only problem as of right now, we need more dirt!  Who would have thought you have to spend so much money to buy DIRT! Here is a picture of my seed transplants after about a week of growth. These are organic tomatoes (beefsteak and roma). We used an egg carton to plan them in. It tears apart when damp and we will just transplant the whole little cube. Then it can disintegrate into the dirt.