Thank you very much for the answer. I understand, dynamic prices (daily prices) are also quite ok and that the prices change depending on suppliers and purchasing conditions. But I find a 140% increase crass and somehow not really trustworthy.

Due to different purchasing conditions and changing suppliers over a certain period of time, price changes/fluctuations may occur. We generally work with daily prices. If our purchase price increases, unfortunately the sales price for our customers also increases.