Stripe currently supports 14 languages, 30+ countries and 135+ currencies. WP Simple Pay lets you set the locale (language) for your payment forms as well as the preferred date format, currency and currency format for your site’s region.
French/Euro One-Time Set Amount
Here’s a demo with an alternate locale (French), date format, currency (Euro), and currency symbol position (right).
French/Euro One-Time Custom Amount
Here’s the same locale and currency settings applied to a custom amount input.