I understood exactly what you meant. There have been many threads about this issue. Your use of t() in that manner violates Drupal coding standards - t() is not to be used to translate variables, it is only for string literals. Translating variables has always been a problem because of this, but no module other than Ubercart makes extensive use of variables, so this translation problem was largely unaddressed in Drupal. The solution is provided by the i18n module, and patches to Ubercart were made so that i18n was informed about all Ubercart variables. Then patches to i18n were made because it was doing the wrong thing. This should all be working now in RC7 with the -dev version of i18n. Follow the links in the FAQ that I mentioned to learn more.