[dalke]

"get awareness among developers for hiring"

Certainly. So is giving everyone £25 for showing up to a meeting. Remember, your reference £9,000 is only paid out when you've actually hired someone. How many hackathons do you need to sponsor before you have an employee?

(While there may be a secondary marketing advantage if the attendees of your hackathon are also potential customers, most likely that's not the case. And of course, there are additional time overheads for any route.)