How to determine the value of an item or occupation post-collapse
People think of things as having some intrinsic value. Take for example diamonds or gold. We all assume that these items have a worth because people desire them. In truth they are valuable since they can be utilized as money since they're universally desired, and so they act as a medium of currency. While gold has a high value as in electronics conducting, this will probably have little value post-collapse. It has been however a jewelry material as have diamonds historically. Still both are not really essential for 99% of people post-collapse who are barely eking out an existence in the short-term.
Some items can be reproduced. Think agricultural products first. Food items, particularly complex carbohydrates and animal flesh are essential to 100% of people, and so learning how to grow and preserve them are essential and hence make them have a very high trade potential. Soybeans produce valuable protein. As hunting diminishes from over-predation, and as trapping plays out from the same, then protein will post likely come from this and animal husbandry. Both require skills, seed, weather, and luck to generate.
Making a quern is a very valuable skill. Bread can't easily be made without a means of creating flour. It takes a lot of work to create flour, and one can easily use up more calories than generate by consuming bread in the process. Millers will end up making money in the long-term. These operations were usually one per village. We don't need lots of stone masons to make querns, most likely this will be a family operation.
Some items can be constructed from Nature's bounty. Tools are essential items for 100% of people, and many tools can be fashioned from wood or bone or shells with only a modicum of skill and effort. Some tools can't be easily fashioned because they need forging, but some enterprising person will have that skill, and most likely will harvest scrap and or railroad spikes to produce knives. Other people will repair tools by replacing handles. Some people will sharpen tools.
There are two most common vices in society: tobacco and alcohol. Tobacco can be grown, harvest, and hung to dry, then packaged for sale. Paper constructed from plant fibers, but more likely will pipes be made from wood or corncobs. Low concentrations of ethanol can be made from apples, but it takes awhile for orchards to be planted and grown. The same is true for grapes, but they require even less time. Corn and potatoes can be fermented and used in distilling operations, but in history many people who drank these products went blind from other chemicals likewise produced from similar distillation temperatures. Since chemical testing will not be in use, but since people will drink regardless, ethanol operations will flourish.
There will be a great need to distill rubbing alcohol for medicinal reasons. Both kinds of still can easily catch fire since heat is used for distillation.
Items which involve fire generation will have high value. People who can produce chert and steel kits; people who can make torches; people who can make tallow and candles from most likely animal fat; people who grow wood will all have trade items of high value.
People who can dig wells will be able to trade their skills for goods. People who can set up biosand filters will too.
Many things will be extremely difficult to replicate post-collapse. Either parts will not be available and difficult to fabricate, or impossible to fabricate. The only way to acquire them will be by cannibalizing old equipment and having the know-how to assemble them and ensure their operation. Still, many of these will likely be luxury items, and 99% of people won't be able to afford them, not in the short-term.
Making gloves and shoes will be necessary items. Both can be made from leather. Shoes can be made from discarded tires. So can roofing shingles and those will be essential.
As preppers, you must think, “Can I learn skills to do these things? Can I replicate them? What is the lifetime value of something? What would someone be willing to trade for them?” What is valuable today, might have very little value in the future.
Think much longer than a bugout bag. That's looking to the first 72 hours of life. What will you do later? If you're not think way down the line, then all you have done is postpone death for three days.