Tapco used to make SKS bolts (not carriers) for $89.99. However, to have someone reverse engineer, design, machine, test and repeat would cost a great deal of money and time. If you could absolutely guarantee 100 or more sales, sure it would be cheaper. But anything less would cost a small fortune getting it right. Machining and 3D printing are not cheap, and are very time consuming. Also, looking at an SKS carrier, you have at least half a dozen milling setups/operations required, and a lot of material (likely pre-hardened to save time and NCRd parts) to be removed. Doing it right is not at all cheap.