Are "Organic" FB Page Likes Even Possible Anymore?

Our fan page has 75,000 likes. We have been running an ad campaign ($10/day) so I assumed a lot of the likes were coming from that. But we have also been busting our hump to create awesome viral images every day. They get shared all over and so I assumed that some of our growht was organic based on someone seeing the page name, agreeing with it and liking it (like it was in the heyday of organic FB page growth).

But when I looked at my Insights, here's what I see:



So basically all of the non ad-driven likes add up to about 4,000. I could get that many likes for $20-30, but have spent countless hours making these awesome images. So basically my time could have been better spent just upping the ad spend and taking less time to create quality content.

I feel like this is a bi-product of Facebook wanting to increase ad spend and decrease organic growth. But I'm not a conspiracy theorist so I will stop there.

Does anybody have any tips for organically growing a fan base? Promotions? Likes from a website rather than Facebook itself?

Edit: Though I guess the quality content is necessary to build trust and increase EdgeRank, so I guess it all works out