Why does dirt cost so much???

I know that landfills charge a lot of money to take dirt, if they will even take it, because it takes up room and they worry about it having toxic content. But where do soil companies get dirt and why does it cost so much? It seems like the quality of garden and potting soil that you buy in big box retailers gets crappier all the time, too. I can't believe the amounts of sticks and other crap that is in potting and garden soil you can buy in bags, yet the prices keep going up. I can see why someone would be drawn to taking free dirt because not only is it free, it's actual dirt. I paid $5 for a cubic foot of Miracle Gro "organic" potting mix and it's dyed brown garbage with very little actual dirt in it.

As for weed seeds, you can get weed seeds from anywhere, not just new dirt. I've wound up with English ivy, blackberry vines, chicken weed, star thistle, and all kinds of hard to get rid of weeds in my yard and haven't added soil in those areas in years. You can get all kinds of things from birds and the wind.