Codecademy's entire funnel was built for self-serve subscription — start free, upgrade later, cancel anytime. Bootcamps were the opposite: one upfront payment, fixed cohort dates, weeks of commitment.
Cash prizes were bringing in referrals from a few dozen people. The question wasn't how to pay them more. It was why nobody else was referring?
There's usually one behaviour that separates users who succeed from users who churn. We found ours in the data, then built triggered journeys to get people over the line.