Lights are very important to those that ride at night. It is a safety issue. The brighter your lights the less chance you have of being run over like a toad. Making lights brighter or smaller or lighter or with longer run time costs more money.
If you have seen an HID in action, you will understand. I do. None of this can be run on a spreadsheet, but $500+ is not that much for some for years of what they believe is more safety.