The difference in fees between 0.5% on a vault with 2000 tez and 20 kUSD is significant. This is because the amount of tez is much smaller than the amount of USD, so the fee for the tez vault is significantly lower. Additionally, the USD amount is much larger, so the fee for the USD vault is much higher. This difference in fees can have a significant impact on the profitability of a given investment. For example, if an investor is looking to maximize their return on investment, they may choose to invest in the tez vault due to its lower fee. However, if an investor is looking to minimize their risk, they may choose to invest in the USD vault due to its higher fee, which could potentially provide more protection against losses.