Idle workers still cost money

Workers who are assigned to a job should not cost gold if there's no work to be done. For example: workers assigned to a mining job without designated ore should not cost money. Right now, my incentive is to take them all off those positions when I'm going offline, since they only cost money and do nothing if there's no designated ore.

Otherwise, every time I come back, my bank is empty and for nothing.

They don't.
Maybe you have farmers, they cost gold infinitely.

I always build up treasury before i logout.