I certainly have experienced the situation that you are describing, where I managed to do tons of D.I.Y. jobs around the house when I really didn't want to call the insurance people because I was sure I'd missed the deadline, but...

I'm not sure I understand why you are requiring a deposit. Is it just to ramp up the "must do this"-ness of the task?

Scenario 1: Your customer wants a huge task so they can avoid it and do lots of other little tasks. - Effective cost: $550 for big task.

Scenario 2: Your customer wants to get good at actually doing tasks. - Effective cost $50 for big task.

Your deposit rewards actually getting tasks done. Is that what you're trying to achieve?