On one side we got an Indie team developing Terraria, which is a game rather easy to add content to.
On the opposing side we got a -blam!-ing huge team developing a game that is rather not so easy to add content to. (Probably)
Before you said that Terraria is easier to add content to therefore the expansions are with more content, keep in mind that Terraria is being developed by a tiny group of people, while Destiny is developed by a whole company.
[b]New Terraria 1.3 Update changelog:[/b]
[spoiler]I couldn't copy and paste all of it. So here is a link: http://forums.terraria.org/index.php?threads/1-3-changelog.20617/ [/spoiler]
I don't think I need to add the stuff added on the Destiny expansions, we all know what they were.
Oh, by the way, that Terraria update was 100% [i][b]free[/b][/i].