Single stage? Is that one pull of the lever equals one finished bullet or just one step in the process?
There are progressive loaders that do multiple operations per pull of the handle. Some are manual indexing, others are automatic. The Dillon RL550b is a manual index with 4 stages. Some of the larger loaders can have 5 or even 6 stages to incorporate trimming accessories or having separate seating and crimping dies. I've even seen it where some folks will use a sizing die as a final stage just to ensure the case didn't bulge during one of the other operations.
Attention to detail pays off big.