You'd think there would be some stops in place like if a change will require an increase of more than X% over the initial planned budget it gets reviewed by som

You'd think there would be some stops in place like if a change will require an increase of more than X% over the initial planned budget it gets reviewed by some independent body that can say "no, that's dumb, stick to the original plan." Planners need some room for discretion and sometimes unforeseen issues arise, but you can't leave final decision making power in the hands of someone incapable of saying no to absurd requests.