It's because it has 80,000 images, multiplied by 14 thumbnail sizes and two file formats. The videos are actually only a small proportion of the file size, because I am currently only doing mp4 and two sizes of ten second parts.
Serendipity is what I'm going for - I've spent about $60 over ten or more purchases while developing the site. Stuff I just decided I have to have.
Actually, I have a list in my account: Geometry Wars x2, Toy Soldiers Complete, LA Noire, War War 2 Time of Wrath, Rise of Nations, Panzer Corps, Fieldrunners, Rigonauts, Bulletstorm, ShaderTool, Tradewinds x2, Knights & Merchants, Dead Space, Crimsonland, Wings!, Imperium Romanium, Hero Siege, Robocraft. Wowee. Most projects go into the red based on server costs, but not this one :)