Top-most business benefit of Cloud is almost zero upfront infrastructure investment:
If you have to build a large-scale system it may cost a mamoth amount to invest in real estate, hardware (racks, machines, routers, backup power supplies), hardware management (power management, cooling), and operations personnel. Because of the upfront costs, it would typically need several rounds of management approvals before the project could even get started.
When you adopt cloud, with utility-style computing, there is no fixed cost or startup cost.
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