Assess the Lay of the Land
Hold off on the reply button a bit longer and don't barge into the VP's office just yet. Look around your organization to see how information flows up. Can the newest programmer sit down and talk to the VP of development? Does communication follow the org chart? What happens to people who bring up problems to their boss's boss? Do they get a fair hearing without retribution? Or are they sidelined forever?
If your organization communicates only along the chain of command, work the chain. If you hit a brick wall at the first level, you need to decide how important it is to you to push the issue further. Is it worth having your boss chew you out? Is it worth losing your job? I'm not saying those responses are right, but it is the reality in some organizations. Look around and decide how much it's worth to you.
Some organizations are different in different areas. I worked in one company where it was okay to skip levels in the development organization, but not in the test organization. The key managers in the test organization were ex-military. In the test organization, issues went step-by-step up the chain of command or they didn't go at all.
Speak the Same Language
State your position in a way that maps to management concerns, and in language they'll understand—which usually means money. Going technical on a manager who has never worked in the technology arena will cause his eyes to glaze over. First, identify one-time costs like development, testing, additional hardware or infrastructure, documentation, conversions, and rollout. Then list ongoing costs: continued maintenance and support, modification of new versions, licensing agreements, and so forth. Don't forget customer-related costs and consequences.
Do Your Homework
Don't just walk in and say, "Hey, this will cost a lot." A complete cost analysis isn't necessary; some level of factual information is. If you aren't fluent in budgets and capital expenditures, find someone who is knowledgeable to coach you. If your manager is supportive of your efforts, she can help you with fully burdened development costs, equipment costs, or license costs for the product you work on. I have found that the folks in accounting are often quite happy to explain how budgets work.
Sum up your findings in financial terms and lay out customer consequences. Take a little trouble preparing how you will communicate up the chain. It may take a little while, but if you do it right, you'll look like a leader and you may save the company a serious misstep. When the SalesSupport team showed the VP that it would cost $2 million to migrate existing customers to the ClientMaster(SM) database, he changed his mind.