I once source for a photographer for an aerial shot. Its about $20k plus. Yes, you have to rent a heli and the tripod is mounted to the flooring of the heli. Even the photographer is trained and there are not many in sg... as for the equipment used, I'm not too sure as my client chickened out when I told him of the cost.
Aerial shoots in SG have to be cleared by SG police before you can even submit to your client. Usually the heli rental company can advise on how to get the clearence or even help you with it for a fee. No special training needed for the photographer as there are no course or test, just briefing by the heli rental company.
A friend just did such a job few weeks ago, special safety gears for him and he's on the ground with the doors open. Another special safety "belt" is attached to his camera. No tripod used. Cost? Heli rental $6K. Photographer $1K. Not sure about clearence as agency took care of it, after the shoot, pass the CF card to agency and bill them for the job.