Shop around and use Google. Costs have gone out the roof since he did his and I will go out on a limb here and say that prices are not going to come back down much. Once they increase prices they stay there and it takes years for our pockets to catch up.
You can research the dimensions of the HID unit itself and then see if you can find another brand with the same or close to the same dimensions that is cheaper. Would stress you also need to research reviews on anything you are going to buy but that should go without saying.