One can piss away a lot of money gardening with little to show for it, especially if you buy bagged soil. Buy a raised planter, some soil, some fertilizer, some seedlings, a couple garden tools and you can easily be in for $150+ which is definitely more than you'll get out of a season worth of growth even if nothing fails.

On the other end of the spectrum, if you grow in fertile native soil from seed your costs can be close to zero