S&P 500 Performance: The VUSA.BE ETF aims to mirror the S&P 500 index's performance. Therefore, the price of VUSA.BE is highly sensitive to changes in the prices of stocks within the S&P 500.

Supply and Demand: General market forces, like investor demand, affect VUSA.BE's price. High demand often leads to a higher price, while increased selling pressure usually lowers the price.

Exchange Rates: Given that the underlying assets are mostly US stocks, fluctuations in the Euro to US Dollar exchange rate can influence the ETF's price for Euro-based investors. A stronger Euro makes the ETF cheaper.

Expense Ratio: The expense ratio represents the ETF's annual operating costs. A higher expense ratio can slightly reduce returns and impact the ETF's net asset value, although indirectly.

Market Sentiment: Overall investor confidence and the prevailing mood in the market can also affect the price. Positive market sentiment often pushes prices upwards, while negative sentiment can trigger selling pressure.