According to the grade of the products you sell, it is divided into medium, high and low grade. What really makes money is the mid-range products, which sell the most, and the low-end products attract customers. For example, if you buy at 100, you can sell at 150. The profit of high-end products should be higher, because high-end products are generally bought in cash, occupying your funds.
If you have just opened a shop, I suggest that you focus on attracting customers, and don't care about temporary profit gains and losses. As long as you have your customer base, it is a matter of time before you make money.
Now that e-commerce is more and more developed, the price will only be lower and lower.
If you buy the price, I don't advise you to sell it on credit at the wholesaler, because the wool is on the sheep, so there will be no advantage if you buy it on credit. My suggestion is to get the goods in cash in the early stage, and don't reserve too much inventory. Now the market is changing rapidly, and I don't know when the price of the products in stock will be reduced.