We are plugged into exactly the same systems for flight booking that Expedia, Orbitz, etc use for flights, so our prices are identical in 95%+ of the cases.
Yes - we're planning an Android app, but for now we have a (we think) very responsive and feature-complete mobile web app, in addition to the iOS app and desktop site.
I'd also echo the suggestion made by the other commenter about having a dedicated page for each trip rather than having to add an itinerary to your own list of trips each time. That page could be more easily shared and could break down costs for each section.
1) Once you create a trip - just click the big red "Invite" button on the right side (desktop site) and you'll get options to invite friends/colleagues by email, share a link where people can see the trip details and decide to join, etc.
2) We just fixed the triplist page so you'll see your cost to book the trip - you ran into an edge case there, sorry!