Before you even bother about whether Giesemann lights are expensive (they are by the way), you should be asking yourself if you really need MH lights.
Consider the following:
1) Size of your tank
2) Keeping SPS or Only LPS/Softies or only a FOWLR tank
3) Running Chiller or not
Anyway, frankly speaking, you have not given any info on your tank set up so just asking where to get MH with stand will get you nowhere since nobody knows what type of MH lights you are looking for. Also what is the temperature (10K, 12K, 14K, 20K) and wattage (150W, 250W, 400W) of the MH you require and the type of MH bulb (Single Ended (SE) or Double Ended (DE)) ?
Anyway, for more information on MH bulbs read the following short write up by Marine Depot.
http://www.marinedepot.com/lighting_metal_...rmation-ap.html