If this happens to you, ea will fix it for you!!! Send them a screenshot by opening up a support ticket at https://simcity-buildit.zendesk.com/hc/en-us/requests/new . They will complete the rebuild for you!
Here are some of their replies:
Thanks for that screenshot, it was really useful!
We're sorry you ran into such a steep order, so we've rebuilt that Residential Building for you, making sure you got to keep your Golden Key reward (taking you from 109 to 110 Golden Keys in total). We're making a few changes behind the scenes to make sure the rebuilding plans are more attainable in the future, so thanks for highlighting this to us.
Hey Mayor,
Thanks for getting in touch. I'm really sorry you've run into this trouble in the game, it looks like our re-building algorithms got carried away in your city! I've passed your experience on to the game team, so they can look at how to prevent this happening again in the future.
In the meantime, I request you to kindly wait for sometime, till we can help get you back on your feet.
Many thanks, and we do appreciate your patience.