The correct choice is Significant economies of scale. AWS can reduce per-unit pay-as-you-go rates because it aggregates demand across millions of customers which enables bulk purchasing and more efficient use of infrastructure.

By pooling demand AWS can negotiate lower hardware and network prices and run data centers at higher utilization which spreads fixed costs over a much larger customer base. These effects let AWS lower unit costs and pass savings to customers which is the essence of Significant economies of scale.

Expand globally within minutes describes the ability to deploy resources across regions quickly and to reach customers worldwide, but it does not explain how pooled customer demand lowers per-unit pricing.

Greater speed and agility refers to faster provisioning and quicker experimentation, and it improves time to market, but it is not the mechanism for bulk price reductions that come from aggregated demand.

Shift capital expenses to variable costs highlights moving from upfront investments to pay-as-you-go billing which is a key cloud benefit, but it explains cost model flexibility rather than the price decreases driven by economies of scale.

Full AWS Practitioner Certification Question