There's an enormous difference between not being able to buy things being built (meaning once you've invested one hammer, you can't buy it) and not getting a discount for rush-buying partially completed structures. Many people seem to make this mistake, so it's worth clearing it up.
Well I was presuming that something that was being built could be moved to being 'not built' but it would still have the hammers in it.
Of course that brings up a Whole host of questions.
If you decide to move something off of the top of the queue... what happens to the production in it?
-stays with the item (CONFIRMED YAY!)
-goes to next thing in the queue
-turns to gold at high rate
-turns to gold at low, standard rate
-lost
If you decide to buy something that has been partially built (when it is not at the top of the queue)..what happens to the production in it?
-discounted cost [indications this doesn't happen, but that would be the best]
-goes to next thing in the queue (hopefully, second best)
-turns to gold at low, standard rate
-lost
If there is more production than the remaining cost what happens?
-goes to next thing in the queue (hopefully)
-turns to gold at high rate
-turns to gold at low, standard rate
-lost
Are there any special rules if any of that 'next in queue' overflow production is more than the cost of the thing next in the queue?
(can things be instatly produced with overflow)
-excess overflow is lost
-multiple things can (must) be produced per turn (hopefully... most sensible)
-excess overflow becomes gold
Will overflow appropriately adjust for production modifiers? [hopefully yes]
Will production be calculated only as integers (so 3 with a 25% bonus= 3)? [hopefully no]