Besides the whole prototype status, ITER itself also has many problems which conflate the cost (and time) required to build. Every country involved wants to make a "significant" contribution, so you get many parts built in different countries, which may need to tool themselves to build these parts, and that need to later fit together. I even think one part had to be rejected because it didn't fit the rest.
The scale is also crazy, inside the tokamak the magnets can push against each other with forces twice that which the space shuttle's launch creates http://www.iter.org/newsline/269/1593
Once ITER is built though, and if it works, then we'll have the knowledge, and tooling required to make more of the parts to build a second (and that knowledge and tooling is spread amongst many countries). The cost will decrease a lot for the first few, and much more after.
The scale is also crazy, inside the tokamak the magnets can push against each other with forces twice that which the space shuttle's launch creates http://www.iter.org/newsline/269/1593
Once ITER is built though, and if it works, then we'll have the knowledge, and tooling required to make more of the parts to build a second (and that knowledge and tooling is spread amongst many countries). The cost will decrease a lot for the first few, and much more after.