The primary alternative to monthly subscription plans is a usage-based pricing plan. In other words, your customers are still paying more than once, but when is

The primary alternative to monthly subscription plans is a usage-based pricing plan. In other words, your customers are still paying more than once, but when is based on how much they use it, rather than per month/year. You could also copy many WordPress plugins, which charge a fee for the first year (which includes support and updates) but then expires afterward. So they can continue using the plugin but won’t get any new updates/support.