Indeed 3G is gonna be quite pricey I expect. For instance, in Poland here's what one popular ISP(who provide land lines+cellphone lines+internet) is offering via 3G
http://www.era.pl/pl/indywidualni/uslugi-porady/internet/blueconnect/blueconnect_noc (Era is a polish version of Germany's "T-Mobile")
all speeds are up to 21Mbit/s (HSPA+) and up to 54Mbit/s(when you connect to one of their "Hotspot" WLAN areas)
2GB/month - $13.8/month(+50 free SMS)
4GB/month - $20.8/month
7GB/month - $27.8/month(+2000 free SMS)
35GB/month - $52.49/month(+2000 free SMS)
also they offer unlimited night quota from 12AM to 9AM (real unlimited quota/no "Fair Usage Policy")
If this was here I would pick the 35GB/month, might sound expensive.. but hey, I pay more than $60/month just for the EXTRA bandwidth I download over my 3GB/month limit so it makes sense :P
they are going to implement LTE there soon, I wish here they would have decided to jump over to LTE quick, but oh well.. guess it's better than nothing i suppose ;/