At a restaurant you trade money against a good meal. Wealth just got created.
You valued your money less than the meal, and the cook valued the meal less than the money. The sum of the difference of valuation is wealth.
Not all trade is equal. Most of the time there is a power relationship where the strong exploits the weak.
An example is sweatshops. People who need jobs are willing to allow themselves to be exploited because they need money. This was common in 19th/ early 20th century before existence of labor unions
how is a sweatshop exploiting anyone if they agree to work there out of their own free will, without the sweatshop they would be worse off.