The farther east in Europe you go, the cheaper it gets. I believe France has the most expensive SIMs and in most Eastern European countries the SIM cards are relatively inexpensive.
I'm beginning to understand this. US phone networks keep us totally in the dark and mostly tied to 2-year contracts, so it's like we're children.
Tell me about it! They also lock our phones! URGH! I hope that lawsuit from the consumer's union (?) regarding the repeal $175 termination fee wins.
So before you head off to Europe, go to this page:
http://www.gsmworld.com/roaming/gsminfo/index.shtml
find the local providers, check to make sure your phone supports the frequencies they have. Then go on their site and see which will give you a cheaper deal, find a local reseller and off you go!
You mentioned Prague.
Eurotel Praha, T-Mobile Czech Republic and Vodaphone are listed as the GSM providers.
Going on Eurotel's site, we find:
http://www.eurotel.cz/jnp/en/home/index.html
Going to their eshop we find
http://eshop.eurotel.cz/eshop/Catalog.aspx?pCat=3
... 3 various Sim cards with 3 various plans, all for under 5 bucks.
Looking at Eurotel Fajn Tariff we find that
Eurotel Fajn Tariff gets you 5.50czk ~= $0.25/min calls to others in Czech Republic and cheap calls to other places in Eastern Europe by dialing *55 before country code and number.
Now I click on
the NetCall *55 link on the page above and then on
More about NetCall *55 and find that USA is located in zone I.
Clicking on
Price Information for this service
I find that the NETCALL *55 Zone price to zone I is either 7.90 or 9.40 per minute, which is still about $0.40 per minute - very reasonable - more reasonable than Cingular.