Producing a programme in high definition is certainly going to be more expensive than if it were a standard definition production so you will have to budget accordingly. The good news is that broadcasters and commissioners know this, and there should be more money available for a programme which is to be delivered in HD. Problems will occur when you are being asked to shoot in HD on a standard definition budget with a view to future proofing or for speculative sale to other markets.
Budgeting for the right equipment.