Hope you don't mind me being frank, but you got screwed. Perhaps there's some complexity that I'm missing here, but this looks like maybe a 200-hour gig, so at 150 USD/hr (you can get real quality talent for that in the US), you'd be looking at 30k. Maybe more if you wanted to put extra time into the mobile experience, but I doubt you'd need more than 40 extra hours for that. Certainly not 100k worth of work here.
EDIT after reading more comments: looks like I did miss a lot of complexity. Still, it's hard to believe all that stuff was necessary. Need more content? Pay some schmuck $7/hr to make content (or outsource on Mechanical Turk, etc). Or stay extra-lean and do it yourself. Admin area? Probably don't need something terribly advanced. Caching? Not unless you're getting a ton of traffic, which it doesn't sound like you are. Wordpress integration? Doesn't sound terribly useful or relevant, but I could be wrong given that I don't know the target market (if there is one?) very well. Maybe you had tens of support emails a day asking for it - but I doubt it.
EDIT after reading more comments: looks like I did miss a lot of complexity. Still, it's hard to believe all that stuff was necessary. Need more content? Pay some schmuck $7/hr to make content (or outsource on Mechanical Turk, etc). Or stay extra-lean and do it yourself. Admin area? Probably don't need something terribly advanced. Caching? Not unless you're getting a ton of traffic, which it doesn't sound like you are. Wordpress integration? Doesn't sound terribly useful or relevant, but I could be wrong given that I don't know the target market (if there is one?) very well. Maybe you had tens of support emails a day asking for it - but I doubt it.