Seems a bit beside the point. I mean, when you go to a hackathon, do you spend all your time telling each other how you hack and coming up with new ways to hack

Seems a bit beside the point. I mean, when you go to a hackathon, do you spend all your time telling each other how you hack and coming up with new ways to hack, or do you actually hack? If there hypothetically were regular sellathons like you describe, I'd probably rather skip most of them and spend the time getting real practice selling. There already are conferences that fill the niche you seem to be thinking of.