Then vm takes if provided the price by the currency
For example, your vendor currency is $, your users can choice between, $ and €. When your users selelcts € and the price is only given in he gets the price in $. But when you provided a price in $ and €, it will provide the price which is set in €.
We have one product in $, the user sees 10$ as 9.x €. When the product has the price provided also in €, for example 10 €, he will see 10 €.