I initially designed my DIY CNC router with 1605 1500mm ball screws. These were inexpensive foreign made rolled C7. No complaints.
Now I want more ipm/speed so I started looking for similar inexpensive 1610 ball screws. The 10 mm pitch screws are 60-150% more expensive for the same class 5mm pitch screw.
I think I read somewhere here its all about mass production. Out of China 1605 has been chosen by them as the one every single factory makes. The 1610, not as many. The nut is more too huh? I've just gone from 1605 to 2510 the nut was us$70 (approx). Alibaba (if you go Chinese) gives you the direct link to the factories. China is hurting presently you might find someone with stock who wants to sell cheap. Rgds