In reality some if not many of the items you set aside for bartering once the SHTF will be used by you, in the days and weeks following a collapse. As the crisis extends bartering will become more prevalent however.
This is not to say that tradeoffs cannot happen at any time, but what do you have that can be parted with in the early days. You have to think long term. You may not need it today but what about tomorrow.
Once society collapses, bartering will become a business, a black market business if you will, likely run by criminal elements. Individuals will have items they can barter with, but in most cases, a person would not be able to afford to part with the items they do have.
Those prepared will probably not need to barter for anything in the early days. Anyone not prepared will have nothing to barter with, so looters will be active as well as desperate people who were previously not of a criminal mindset. Looters and other criminals will steal so they can then use the stolen items to barter with and thus the black marketing of goods will begin.
Even those that prepared for a crisis likely miscalculated the amount of food and water they would use. This means that food and water would not likely be a bartering item unless food could be produced to replace what was bartered or sold and a private well was accessible and reliable, so you could afford to part with drinking water. Otherwise, people will have to hang on to the essentials to ensure their own survival.
In the beginning, everyone will need food and water, and as the crisis extends other items, items not essential to survival, will be in demand like tobacco products, alcohol, clothing, old eyeglasses, diapers, children’s items, reading material, shoes and so on. Over time however, you would probably find that no one would be willing give up a life essential for tobacco or alcohol.
Medications, water and food will be needed by everyone and if you stockpiled medications for bartering, for example, you may find you need them for yourself or family. Medications will be hoarded by everyone and typically, people will only stockpile medications they will need for themselves due to the cost, which means they would not likely barter with them. What medications could you obtain that could save the life of another unless you were a physician with access to life saving medications.
The medications you can lay your hands on now to stockpile will be what everyone else has access to in most cases. If you stockpiled antibiotics from prescriptions you filled and did not use, you may find you will need those antibiotics for yourself at some point after the SHTF.
Some people plan to stockpile firearms and ammunition for bartering, and of course they can do this but it is not recommended. What will they have that you need for surviving that they are willing to part with, because they will need the same items for survival?
So Then What Do You Do and What Can Be Used For Bartering
Instead of trading ammunition that you have stockpiled trade your skills, so this means you should learn how to reload shells. You will of course have to invest in the equipment and materials now. Once you start trading ammunition and firearms, others will seek you out for ammunition and firearms and it will get to the point where your survival is at stake, because if you cannot reload shells then of course your stockpile will deplete instead of being replenished.
You will need the skills of others, as well, so you can trade your skill for theirs. Doctors, dentists and nurses will be in high demand and at some point you or your family will need their services.
Learn how to work metal into knives, and into other useful hand tools become a blacksmith in other words. Once word gets around you can shape metal into usable items, you will be in demand and people will be willing to trade items for your services or trade their skills for yours.
Raise food and livestock that can be used for trade. There are so-called cash crops, as well, that can be raised such as tobacco. Tobacco can be raised in many parts of the country and once all the retail tobacco products are gone, tobacco will be in demand. Raising your own and knowing how to cure it would give you a tremendous advantage.
You can also learn how to distill alcohol but this requires grains and fruits, which would be in high demand and short supply in the beginning, but once food production increases distilling may be a valuable skill to have. You have to plan for the short term as well as the long term.
Clothing will be valuable and knowing how to sew to repair clothing and even make clothing using cloth and leather will be a marketable skill post collapse.
There are a number of things that you can do to obtain what you need without trading items you need for survival once the SHTF. Imagine your child needs antibiotics and all you have for trade is your food and water, and those with the medication need the last of your food and water. This is not a position you want to be in. Learn the skills now that will allow you to not only replenish your stockpiles but can be used to trade for possible life saving items.