[chii]

i read the parent post's advice as duplicating, rather than changing - e.g., you keep the existing domain, but also the exact same app is available from those other domains.

But you're not wrong - i dont think the domain has a big effect, and personally i'd rather save $10.

[dewey]

That’s duplicate content and Google doesn’t like that. You can set the canonical url etc. but in the end the URLs will not make the difference between a user understanding the interface or not.

[n4bz0r]

You simply use 301 redirects on the secondary domain(s).

You can also use secondary domains for landing pages. But that's probably out of pet projects' scope.