/u/3029064 submitted a post to /r/GrandTheftAutoV today titled "How much have you spent on Shark Cards?" It's actually a link-based submission, that points to a Straw Poll. Before I get into how much I've spent on Shark Cards in my time playing GTA Online, I want to go ahead and embed the poll so that you can vote for yourselves.
The Annihilator was worth the buy in my opinion, but I quickly realized that the Buzzard Attack Chopper was actually the better buy after the fact. I still enjoy doing helicopter dogfights, as long as there aren't any rockets involved. Annihilator can still melt through aircraft very quickly. In fact, it's a lot faster than the Buzzard's miniguns.