All charges on DLsite are made in accordance with the currency and cost displayed next to the "Purchase total" on the "Confirm Purchases" page.
After which, the final cost will be calculated at an exchange rate determined by your card issuer, the payment service provider, or the point purchase subcontractor, and converted into your currency for billing.
On DLsite, prices displayed in other currencies (such as dollars and euros) are estimated values based on the exchange rate on the date of the purchase and are for reference only.