"eBay's business is based on enabling someone to do business with another person, and to do that, they first have to develop some measure of trust, either in the other person or the system."
- Pierre Omidyar
What would you like to reassure yourself- fire can burn you or water can quench your thirst? To decide the affordability you must have a log of experiences that can help you crystallize the will to experience.
Scientific evidences are facts and information coupled with principles of inference. They serve either to support or counter an experience. You may be someone who hated green leaves for food. After learning about its health benefits growing out of scientific evidences, you would turn into vegan. In fact, You don't believe in vegetable; you believe in science, you believe in method, in process or in person. You have experienced the benefit of it many a times. You find even nominal cost a wastage. You trust it because you have tried it several times in different cases and found it a track to go on. In fact, you don't find a need to experience it every time. The benefits are satisfying or above and you have reaped out of the method/process/person enough to take a risk. Now it is no more about a single experience but an aggregate one. It is not going to make a big difference in aggregate cost/ benefit.
The decision based on this cost/benefit is function of Common Sense. Your Common Sense about yourself. What ratio you set for Cost/ Benefit to be to take an action or to defer it to an experience.
Have you ever seen a child? Its nosiness in everything what attracts it. It wants to hold the fire in hands, jump in water and bite to eat dirty things. The elders are there as their custodians to have them experience. For that tender mind, we sometimes make an act to show them that it's hot and you will get burned, connecting him with some prior experience of him touching something hot. Sometimes they understand sometimes not.
It's others' experience as well, when the cost is unaffordable.
How many times you don't count on the people you trust most? What they say is the reappearance of their own experiences or theirs whom they trust. So you don't go only by those whom you depend on but even those whom they are certain of. Humanity is surviving on this. You can't afford reinventing the fire or wheel. The cost may lead to misery or extinction. So you rely on the experience of others. You also can not afford to go by the experiences of anyone; it will also lead you to the same. You trust on your doctor for your health issues, you trust on your accountant for finances, you trust your mother for good deeds, you trust your friend for hard times; you trust your college, your Institute. Why Mr. “X” is your doctor, why not Mr. “Y”. Why you work with organization “B” not “A”. Now your experience is important. You have experienced them and you know how sane are they to you and how conforming to your thought process to imbibe and anatomy to execute.
So it's your experience and solely your experience on an affordable cost not only about what you experienced but also whom you experienced and what and whom they experienced. Derivatively it's others' experience as well, when the cost is unaffordable.