[Suicide Junkie]

Another option, is to right click on the item while inside a build queue.

There, it will show you both the price and maintenance.

Be warned: the windows with dual cost showing (price and maintenance), are not guaranteed. If the vehicle (such as a base) or a component is on the vehicle that modifies maintenance, it is not reflected in the dual window.
Once built, the maintenance shown when you click a vehicle is accurate.

I don't know if the latest public patch addresses this, but the next one surely will.