Hi,
Hope you have already installed Odoo community in your local machine and you are looking to Buy the Odoo Enterprise for the accounting , right ? The Odoo enterprise is charged monthly or annually, there is no option to get it for one time payment. If you check this page you will understand the pricing structure of odoo: https://www.odoo.com/pricing
Odoo is charged based on number of users and no of apps installed. So if you bought the system for 432 usd and if you install more apps other than in the license it will cost more. Also this 432 usd will be for particular modules and particular number of users. Better you can connect with odoo over the email and clarify the things.
Alternatively you can also check this third party accounting modules available in the odoo apps store: https://www.odoo.com/apps/modules/13.0/om_account_accountant/
Thanks