The draw.io plugins are actually paid via Atlassian, only Atlassian can generate the quotes and they only provide quotes for annually billing with a trial of the product currently in place, they will not quote for monthly billing.


Go to https://www.atlassian.com/company/contact/purchasing-licensing, click "quotes and orders", "create a new quote", "host in the cloud", then press the contact us button. You fill in your details telling them which plugin it is and they should come back to you with a quote.