I second that. There are many references to ‘developer greed’ in these forums but these guys’ time does not come for free. If you have a problem paying again for DUB, you have the option of not upgrading. It’s possibly a little expensive for an upgrade but you are getting what certainly appears to be a completely new airport. That some devs choose not to charge is testament to THEIR generosity and love for what they do, rather than an indictment of those who do choose to charge for their surplus time.
It’s certainly not as cheeky as some of Captain Sm’s tactics!