GTA Online's most recent DLC not only added the legendary Duke O'Death to the game after years of the vehicle being considered unbalanced, but unlocked the returning player content for all to buy and enjoy, seeing as without character transfers, no more players will achieve this status.

Returning player content refers to a collection of select items and vehicles which were only made available to those who transferred a character from either the Xbox 360 or PlayStation 3 versions of GTA Online over to any of the Enhanced Editions. The vehicles, such as the Kraken Sub or the Dodo Seaplane, weren't given outright to these players, however only they had the option to purchase them.
Now that the vehicles (and the Hatchet, for those of you who remember it) have been made available to all players, Rockstar didn't want the returning players to feel like their loyalty wasn't appreciated anymore. Those returning players who haven't bought some (or any) of the content exclusive to them were given ownership of it for free.
Naturally, this would make those who bought it originally feel more than a little rustled, since others now got the same content for free simply by waiting. However, to solve this issue too, Rockstar has retroactively refunded any and all returning player content fans have bought over the course of the game's run in full.