What is the difference between on-demand and subscription pricing?  On-Demand Pricing
On-Demand consumption allows you to pay for physical hosts by the hour. There are no upfront costs and you have the flexibility to scale the number of hosts up or down without long-term commitments. You only pay for each hour that the host is active in your account. If you choose the on-demand option, you will be billed at the end of the month in arrears.
Subscription PricingPrepay longer-term subscription of hosts gives you up to 50% cost saving compared to on-demand hosts consumed over the equivalent period. Host subscriptions are available in 1-year or 3-year terms. If you choose a 1-year or 3-year subscription option, you can choose to prepay upfront or pay monthly.