60 USD IS MAX
We have a photo app that uses backbone and it's almost the same as "instagram"
We need to implement a "tag" system. So each photo can have a list of tagged users (users related to that post). So when the user is looking a post the post will have a "tag" button, just as the "like" button, when the user click tag button, the user has to type the name of another username on the system and then press enter or an OK button, when the user does that the tagged user appears on the tagged users list. Only the user who posted the photo can tag other users
You'll have to correctly apply the MVC, using eventbus, presenters and views.