I'm beginning to create a pretty advanced registration form that has all sorts of conditional logic in it. For instance, if a registrant chooses the "Diamond" level sponsorship in a list, the price increases $3000 and they're allowed to register 8 players for their team. In this example, I'd want a price field to increase by $3000 and I'd like an 'unlimited value' text field to display 8 text fields.
What's the best route to take when creating an advanced form like this with lots of interactivity? Traditionally I've used EntityForm Types and field dependencies, but I'm not sure how far that will get me.