PortSwigger Web Security: Business Logic, currency arbitrage - Possibility to pay less than the price in USD

Currency fluctuate all the time. Theses days EUR / USD key pair is around 1for1. It was even 1:0.99 when I was writing this report.
Portswigger doesn’t change dynamically the price and exchange rate dynamically.

Vulnerability at the following link: https://portswigger.net/buy/pro

When you want to buy a product choose the currency, you can noticed they are fixed and with today difference it’s quite a big difference.

Impact

USD price is 399$USD, while EUR price is 349$.
Therefore someone could just change the price to Euro and pay 347 $USD (349 Euro) instead of 399$(with current rate).

PS: It scale with the price, it could lead to thousands of dollars lost for your company.