The basic idea for the purchase option is that it will increase in price with every major release.

It started at $10 as a special introductory price and then increased to $11 with the release of 0.1. In addition, each subsequent 0.x patch the price will go up $1.

Subscribing on Patreon/Subscribestar is still the best way to support the continued development of the project. This is for those who have no desire to upkeep subscriptions and want a one time purchase option.

Note: The increases apply to 0.x patches not 0.0.x