I'm a software developed and can confirm that I can't afford the time to fix/improve the software for nothing.
Here's a suggestion for an upgrade policy:
Free updates to the same second level versions - that is upgrades are free for 8.0.8, 8.0.9, 8.0.10 etc. These are generally bug fixes and customers deserve that for free.

Upgrades from 8.0.x to 8.1.x cost a small amount. They should not include simple bug fixes, but are added features. A person with 8.0 can skip updates, and pay just the single update price even though going from 8.0 to 8.4

New versions, ie 9.0.0, are major changes, major new features and power. A new price is set with a discount for current users.

Shareware is a cheap price for software, and no one should expect free-for-ever updates, regardless of what is said. You should expect bugs to be fixed. Bug fixes without new features and with a charge is wrong. What appears to have happened here is new features and bug fixes for a small charge -- that's reasonable.

For those that deleted your previous version and then found there was a charge. You should have been warned about the cost. You should have backed up and be able to restore the previous version. Forgive the author, forgive yourself.