Good SIM for a short stay

[inquisitor]

An AldiTalk SIM card available at Aldi supermarkets would cost you € 12.99 including € 10 credit. 500MB of data valid for 30 days cost € 6.99 and will be deducted from the initial credit.

calls from Germany
to Germany (including mobiles): € 0.12/min
to EU fixed lines and US: € 0.12/min
to EU mobiles: € 0.29/min

EU roaming
incoming calls: € 0
calls to EU: € 0.11/min
calls to US: € 0.99/min

AldiTalk also has an interesting roaming bundle for data in other EU countries which gives you 150MB valid for 7 days costing € 4.99. Once consumed you can reorder a new bundle minutes later. Otherwise data will start to be billed volume-based at € 0.24/MB.
Of course data would be much cheaper if you get a separate Austrian SIM card for Austria.