Upgrading from one Gunbot package to another is not more expensive than buying the target plan outright. There may be tiny differences in price, but in general the upgrade costs just the price difference between two plans.

Most upgrade options are for lifetime plans, that's why there are no recurring costs.

To 'upgrade' from a monthly plan to a lifetime license, you can just cancel the subscription (when paid on paypal, else there is no automatic renewal) and place an order for a lifetime plan. There are no specific upgrade options for this.

Gunbot uses a system to validate license ownership through the blockchain. To do this, it uses a utility token called "GUNTHY" that runs on the Ethereum blockchain. The goal of this system is to not depend on a central license server. An added benefit is that you can even sell the tokens when you don't need the software anymore.