Hm, actually sorry I assumed they had made vizier available as a blackbox service (https://static.googleusercontent.com/media/research.google.c...). If they haven't, you can save money/time by employing better than grid search. There are some re implementations of vizier available, I'll see if I can make ours too (email in profile). I do agree with that billing can be..complex ;)
Cloud ML Engine is a bit opaque in terms of price efficiency (how powerful is a "training unit"?) but I suppose that's another option.