Use logic, AC : GSOC is only worth it if the rewards are higher
GSOC is only worth bothering with if it leads to a job, or it's not about money. Google is using it, in part, to identify people to recruit.
Therefore, people will aim at the more popular projects, and won't bother with the piddly ones.
The students have three months to write the code in, it is to be presumed that the task isn't trivial. They are paid 4500USD.
I don't know what temporary work pays in the US, but in the UK 4500USD over three months is not far from the national minimum legal wage (i.e. for crappy jobs). Temporary work from agencies tends to pay higher than the minimum wage. Coding work should be priced considerably higher.
So, if it's not going to lead to a job, you're asking them to give up the best months of the year, doing something nerdy, missing out on exercise, holidays, alcohol, sex etc for poor pay. Wow, that sounds *SO* attractive! Your only hope is that they're contributing to something world changing, or something that is a Calling rather than a job.
(Actually, it's even worse than I mentioned, because in total it spreads over more than three months)