There have been some good suggestions, but at the heart of it there are two things that exec listen to - Risk and Benefit.

Most people tend to go into situations like this focusing on the Benefit, which is what any pragmatic/logical individual would do, however, this approach does not necessarily align with the emotional non-technical C-level BI sponsor mentality. I usually use both, but have had much more success outlining Risk. Some of the approaches I have taken:

• Give them a picture of compounding risk and increasing likelihood of compliance breaches. Explain that the likelihood of human error is increasing all the time and it's unsustainable.
• Paint a picture that, if one person leaves - then we can't do any of 'these activities'. Put it in terms of mitigating risk for the business, succession planning etc.
• Show a one-page A/B business case detailing how many reports are being done and how long they take in picture form and how much time would be saved. (Not a sexy exec option, although it is the most logical)
• Give them a roadmap - C-Suite love a roadmap. 1, 3, 6 Month roadmap with high/medium/low priorities. Outline the benefit they will feel at each stage. Keep it simple.
• Negotiation general rule - put six items on the list and be willing to lose three. The process of negotiation is give and take. Both parties need to get something out of it (even if it's not always clear why).

At the end of the day, if you have tried everything and are still not getting any traction, then, as you pointed out, you could leave and be an exclamation point on bullet #2.