It's not a traditional auction in the sense that "highest bidder wins". The goal is to present each software engineer with 5-10 opportunities at cool companies, with numbers attached to them.
They can then choose which offers are worth following-up with via phone or in-person interviews based on any number of factors (location, product/service, company stage, who the investors are, equity, salary, etc.).
Like you say, there's much more to a job than a salary but in an environment where the average SF Developer gets recruitment spam every 40-hours, we hope to provide a more efficient way of vetting & comparing opportunities.