Monthly cloud service costs are BEST described as:

Monthly cloud service costs are best described as operating expenditures. Operating expenditures (OPEX) are the ongoing costs of running a business or a service, such as rent, utilities, salaries, maintenance, and subscriptions1. Cloud services are typically paid on a monthly or annual basis, depending on the usage and the service level agreement. Cloud services reduce the need for capital expenditures (CAPEX), which are the upfront costs of acquiring assets, such as hardware, software, or infrastructure1. Fixed expenditures are the costs that do not change regardless of the level of output or activity, such as rent or insurance2. Personnel expenditures are the costs of hiring, training, and retaining employees, such as salaries, benefits, or taxes3. References: CompTIA Cloud Essentials+ Certification | CompTIA IT Certifications, CompTIA Cloud Essentials CLO-002 Certification Study Guide, Fixed Costs Definition, Personnel Costs Definition