This is due to a new update — according to this answer, it partially reverted to an earlier behavior.
Edit: I'll quote that answer about how prices are calculated:
the costs associated to Imperial item building have also changed, apparently in proportion to the time required.
It is very annoying because the imperial missions that were active at that time require a ton of those. The reward will not cover the costs (by a long shot).
Some subsequent missions are no better, which is indeed annoying (cannot show an example now).
However, skipping them costs 10 bux, which is also a lot.
For me, this seems to have started with the update which introduced the new mission system, together with the promotion for imperial medals (though I didn't notice the prices were so high, so maybe it was not the case then).
Edit 2: the prices seem to have dropped back to "normal" (around ~1500/2000 bucks tops).