I think by saying "just money", you've pulled quite a trick. Not only do you implicitly dismiss the opportunity cost of one's own time better spent elsewhere, but you also assume away the problem of having enough land to develop, the capital cost of this land, the opportunity cost of not using it for other things, not to mention the risk costs of weather and disease - there was a pretty bad potato famine back where I come from 150 years ago, you might have heard of it.
If you're going to bring opportunity cost into the equation, don't forget the physical and mental well-being that comes with gardening. That hour of daily digging, squatting, etc. might very well offset a daily hour at the gym or reduce physical issues associated with a sedentary lifestyle. Also, the satisfying act of gardening might very well reduce one's need for drugs and therapy for mental problems, which, sadly, are all too common today.
Sure, just money.