There definitely are people who spend lots of money on their gardens, so not far off in some scenarios. I am fortunate enough to have a trailer, but if I didn't it costs about $100 for a load to be delivered. I get it ~2 times a year, so it can get pricey. Even what I do, if I were to pay myself minimum wage, it would still be much cheaper to buy it from a store.

For sure, it depends on your location and your soil type, and likewise compost/fertilizer use. The stuff from the landfill is really good stuff, I was quite skeptical at first, but read how much care and testing they do to ensure it meets standards for food growing use. They produce a yearly report with contaminant/foreign debris levels, and they are much lower than the government requirements.

I was not having much luck with onions, oddly enough, while my neighbour didn't know what to do with them. I live in an area surrounded by trees, so I don't get direct sunlight all the time, which kind of makes it challenging.

I don't think what I grow is "sellable," so I just give it away to friends an neighbours. I've only been growing for about 2 years, so still need some practice to get the right shape/size vegetables. At that point I might be a bit more comfortable having someone give me some money for it :)