Board Thread:Game Discussion/@comment-11297866-20130628113213/@comment-11297866-20130628123056

Brimstone 747 wrote:

Although you can gather resources to upgrade cards, I do not advise anyone to upgrade any cards during event downtimes. The reason being that it is twice as expensive, and takes double the amount of cards for upgrading. Cards used for upgrading gain an invisible 2x bonus during any event, so waiting till an event starts to upgrade anything will make your "upgrade fodder" twice as effective.

The only exception is trans metal. Trans metal and weapon metal costs the same amount all the time to use. This is very good to know! thank you!