[tcbawo]

This contest seems like the equivalent of the "inventor's hotline" infomercial. If it identifies one promising new approach that they can iterate on, it has probably paid for itself. It also serves as a good PR and recruiting tool. The prize is probably designed to bring in clever non-professionals. It's a win-win for Jane Street

[elil17]

The inventors hotline infomercial is a scam where they get you to pay for expensive patent filing, consulting, and marketing packages. They never intend to actually use any of the inventions.

[Traster]

If someone has a good idea, you don't want the idea, you want the person. If you take the idea, at best you'll split the market with the person who had the idea. At worst they'll iterate and you'll get nothing. Far better to find people who have the skills to develop an idea.

Having said that you also want to find the (vastly more in number) people who can take someone else's idea and actually implement it.

[amznthrwaway]

I sincerely doubt they think they'll get actionable ideas. It seems like a fun recruiting play from a company that takes pride in hiring non-traditional talent.