You don’t have to hack the currency filter!
AngularJS has a great support for i18n/l10n. The currency filter uses the default currency symbol from the locale service and positions it based on the locale settings.
So it’s all about supporting and setting the right locale.
<script src="https://stackoverflow.com/questions/27547680/i18n/angular-locale_de-de.js"></script>
If you are using npm or bower all locales are available via the angular-i18n package.
<span>{{ product.price | currency }}</span>
will now produce the following output:
65,95 €
Supporting multiple localizations
If you want to support multiple localizations be careful with the currency symbol as it changes to the default currency of the used locale. But 65,95 € are different to $65,95. Provide the currency symbol as parameter to be safe:
<span>{{ product.price | currency:'€' }}</span>
In de-de the output would still be 65,95 € but if the location is eg. en-us it would be €65.95 (which is despite some other sayings the correct format to display euro prices in English).
To learn more about angular and i18n/l10n refer to the developer guide.