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.

Gunbot is not a subscription service, that's why there are no recurring costs.

Any upgrade to Pro or higher does include the Backtesting add-on.

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.