If you aren't made of money, I have bad news: Customizing knives is for people who are made of money.
You'd be lucky to get a set of custom scales for less than the full retail price of a Delica. When you consider time, labor, and materials, it's entirely unlikely you'll be able to get anything but plain G10 scales for less than $70, especially with the milling and the finishing and the...
I imagine there just isn't a big enough market for custom knife handles to support high-volume low-cost aftermarket parts production for production pocket knives. Remember, most people don't even know this whole world of knives even exists, and out of the select few that do, even fewer go for custom parts. We're talking tiny fractions of a tiny fraction of a population. Not much to build a company on, but enough to support individual hobbyists and suppliers.