Well if you think about it. It's not really that bad.
500 gallons of solution for a hundred bucks. That's 100, 5 gallon buckets of solution. That's a dollar per 5 gallons of solution to feed your soil.
That means I can put a gallon of solution in my 5 gallon pots of soil grown plants.
So if I have five plants growing in 5 gallon buckets, I will use 5 gallons per feeding every couple days. That's a dollar per feeding or two dollars if you double the strength.
So if you feed 3 times a week. That would be 3 dollars a week.