Ultimately, the price difference is what the manufacturer can charge for the knife the people are willing to pay and will net the manufacturer some acceptable profit (who's expenses are well beyond the cost of raw materials for the knives).
That said, though, the factors that seem to contribute most towards big steps up in price are:
- Blade steel - This seems to have the most consistent and significant impact on prices. Edge retention is probably one of the biggest differentiators, but there are many other properties (toughness, stain resistance, hardness, grain size, etc.). This isn't remotely close to being an exhaustive list of steels, but some common ones include: low cost - 420HC, 440A, 8Cr13MoV ... moderate cost - Sandvik, AUS-8 ... high cost - VG-10, S30V, 154CM ... really high cost - ZDP-189, Elmax, S110V
- Handle materials - Most materials don't seem to have a big impact on knives, but there are a few that tend to drive up the cost quickly. Stuff like plastic, FRN, steel, aluminum, and G10 don't seem to affect cost much. Some natural materials (eg. bone or wood) can have noticeable cost impact if that particular is uncommon or scarce. The premium materials I can think of that significantly drive up costs in production knives are titanium and carbon fiber.
- Brand/manufacturer - This is more difficult to quantify, as it doesn't directly track to materials, designs, fit & finish, or anything else that can really be measured looking at just the end product (ie. the knife) itself. This falls more on the business side. Each company is likely to have different business costs (eg. employees, equipment, property, licensing, etc.) and different profit goals (eg. target margins for each product sold). All those get factored into pricing the product. Also, there's just plain ol' branding. Some brands will charge more for their name simply because they can and people will buy it (reputation, pride of ownership, or any number of arbitrary rationales).