sometimes they have them. you could feed him frogs or crawdads you catch down by the river. Id start my own worms ranch. get a 5 gallon bucket and fill it with dirt and throw some ginormous night crawlers in it and let them make lots of babys
Keep a variaty... and talk ahead with your LFS. Ask 'em if you can buy 500 crickets at near cost/minimal profit if you order with them from their supplier thru them at teh same time. Same with feeders (how much are fancy guppies or danios? likely less nasties than feeder-intended fish), etc. Or grow your own convicts, guppies, etc.
No it can be really cheap if u have a good supplie of waste food for them. Table scraps ex ex ex. I have a few fruit trees that i use for food on my box. They like oranges n apples. Best thing is to do is make a little hole... toss the waste food in and cover it back up. Watch out the smell can get harsh at times lol.