Wow, you've managed to simplify the concept even more! I guess the lack of money transfers limits this to non-continuous cases tough. (Which might be just fine)

I like the fact that the "landing page" is the tool, hopefully this stays with the finished version also.

This could be just due to the unfinished status, but currently at least it does require awful lot of clicking around with mouse. At least entering the cost of an item right after the name should be possible without touching the mouse. (and it actually took a moment for the first time to notice that you can edit the cost afterwards)

Maybe it would be also good to make a more drastic graphical difference between the names and the items?

Are you planning on adding possibility to mark certain items to be paid by certain people only?