That might be related to the fact that the original whatsapp software compresses/scales down images, while yappari just sends the original file. If you put your phones camera to full resolution, the resulting file might be a few MB big. I got my camera set to 1.3 MP and thats more then enough for snapshots actually and the data usage is hence lower, as the image is only a few hundred KB big.

So if you are sending photos like a champ with Yappari I get the idea that you are needing a more then 1 GB internet package. But on the other hand: I am even using Yappari in roaming networks in the EU on an EU sim card, where a MB is 0,49 € (while roaming) and even for a few days connection without a lot of multimedia transfers, I am paying a maximum of less then 5 € for the whole thin, probably even a lot less, so if you really need more then 1 GB in a month, you should rather check other applications using bandwidth, too...

Cheers