Quick answer: definitely more than by pestering people to work for free.
Longer answer: Please treat it as a guesstimation, I'm a hobbyist and the following is largely just how I would see it.
I think that one of the ideas that seemed feasible was intended to help people find cheaper prescription drugs depending on location or generic option if available. There does not seem to be something like that in our market and it seems like there is a niche for such service. What you could likely expect:
- the skeleton of the website,
- some bare-bones account functions,
- a prototype of the database that would be a backbone of this whole endeavour.
If you could provide access to data from pharmacies beforehand you could likely get:
- information about closest pharmacies that could handle your order based on geodata (Geofabrik helps a lot with it),
- at least some of the actual data in that database.
Don't take it as a definitive answer, I have no first-hand experience with such project and that's pretty much what I think that I could be able to do if given a few months. I'm likely underestimating the challenge by a lot, but the problems come during development. Having these 15-20 people, many of whom have at least some basic experience or work as programmers, would provide you with at least a number of solutions to choose from.
Would it be an amazing deployable solution? No.
Would it be deployable at all? Not straight after hackathon, you would get a rough prototype at best.
Would it work? As well as a prototype can.
Would anyone want to work on it later? Most likely. Nearly all hackathons get some sort of continuation, some get revisited by a whole group out of interest. Plus by having some sort of codebase you would be saying "I have a prototype that came as a result of a community event at <name of university or hackathon> and need someone to help improve and polish it" and not "build me it from scratch for free". That's an entirely different message.
It would not be a finished product at all, but that's at the very least something to improve and build on top. You would get at least more than by basically begging complete strangers to do you a solid.