Hi,
When we released OnDemand and supported multi-currencies for the first time, we made the decision to just support the basic service, which is what the majority of users take. We then figured we'd see which currencies were most popular and then program all the add-ons to support that non-USD rate. We just aren't quite there yet so if you need an add-on for OnDemand, you'll need to switch your account to USD, then you'll be able to add anything else we offer on OD.
Thanks.