One of the reasons for the high cost of food, that is meant to last during long term storage, is spoilage. It costs more to package the food to keep it from spoiling while it is stored for years.
The two main problems that must be dealt with for long term food storage are oxygen and bugs. If you can get all of the oxygen out of the food, and keep it out, that will usually also eliminate the bug problem.
It will save you a lot of money to package your own food instead of buying food that someone else has already packaged for you.
This is going to be a lot of work and you may decide that you need special and perhaps expensive, equipment to prepare your food for storage.
I have watched videos where people have done their own food storage without a lot of expensive equipment. The main equipment they used were a clothing iron and a bicycle pump.
They also used some supplies. These were large plastic buckets with tight fitting lids, mylar bags, and oxygen absorbers.
I have sealed some of my dried foods that I dehydrated myself, using even less supplies and equipment. I kept some of it in storage for as long as three years and it was still good.
The equipment I used was a clothing iron. I used recycled plastic bags for supplies. I did not even use a bicycle pump to get the air out. I simply squeezed the air out of the plastic as best I could.
I cut the plastic bags to the approximate size of the food to be stored. One side of the plastic was folded over, leaving only three sides to seal. I sealed two of the remaining sides of plastic before putting the food in it. Then I squeezed the air out of the bag as well as I could manage and sealed the remaining side.
I suggest that if you want to do this, you practice a few times on pieces of plastic, before you involve any food. It takes a little practice to know how hot to get your iron and how long to hold it on the plastic.
This post is getting too long, so I will continue it.