Concur entirely with FRANKENMAUSER!
As I have contact with folks who work at the REM plant, I can say certain cases, components, and loaded ammo is made in batches and maybe once or twice a year or once in 2 years.
Rem makes annual and limited runs only of less popular items to fill stocks as requested by wholesalers. Less popular cartridges such as 35 Rem, 303 Brit, 8x57 fall into that category. Winchester is no different.
When existing stock is consumed, buyers must live with the law of supply and demand until a new run in manufactured.
On the flip side, popular components such as 308, 223 are in constant production.