You refactor your product to need as little customization as possible, and make it easy to extend and modify. The more OSS you can build on, the more money you save. One IT employee is easily $100K/yr after benefits, so if you can eliminate that much custom work, that's what you can charge. I'm not saying that this is easy to do.
I was thinking that understanding the problem (the business's "IT needs") is hard to commoditize, and can't be done with 100% automation (unless all businesses were cookie-cutter, automatically formally describable - perhaps almost true for some franchise-style businesses).
